Laptop Reboot on Startup

Have you considered a Exorcist? Have you cleaned the fan, vents, heatsink recently? Take a look at this it may help in troubleshooting: http://www.youtube.com/watch?v=2Yi6GNFcP3w

First - re-seat the hard disk and reboot the computer. If the computer does not boot up then reboot and go into the BIOS configuration to see if the BIOS detects the hard drive. If it doesn't detect the hard drive then it could be faulty.
Then the hard drive needs to be replaced in the computer/laptop, Windows installed and the computer or laptop's device drivers plus your programs etc. to get a functioning computer/laptop again.

OverheatingWhen the CPU overheats then it will shut down (i.e. thermaloverload) and won't boot up again until it has cooled down. If this is theproblem is not fixed then the CPU will eventually fail.
A faulty fan causes the problem or the fan and heat sink assembly are cloggedwith dust.
Check the CPU fan to see if it spins freely, if not replace the fan.
If the fan and heat sink is clogged with dust the remove the dust and make surethe vents are clear and dust free. Use a small brush and can of compressed airto do this.

When turning your laptop on, before Windows starts booting, a splash screen appears first (usually with the logo of the manufacturer). Look on the splash screen (usually at the bottom) for a key (usually F10 or F11), assigned for System Recovery CD/DVD with the laptop. or 1.Press the start button from the start menu depending on your operating system(win 2000,xp) 2.Press Ctrl+Alt+delete combination from the keyboard. 3.If you have a power button on your laptop keyboard,it could also be useful by pressing and hold it down for few seconds N.B: "Ctrl+Alt+Delete" can exit you from usage and trigger a reboot or shutdown. Try and reboot using the operating system. Attempt to use the key combination that will allow you to exit from the operating system and restart the laptop. Be patient, as it may take some time if it has locked up. Hold down the power button. If the operating system's answer to the rebooting will not work, find and hold down the power button of the laptop. This should cause the device to shut itself off. You'll have to press the power button again to power it back on, completing the reboot. Unplug from the wall and remove the battery. If restarting via the operating system and the power button do not work, unplug the laptop from the wall outlet, and remove the battery from the laptop. This will cause it to power off immediately. Allow time to reboot. Give the laptop time to cool down before you power it back on if you had to do this manually. A few seconds should do unless you have additional problems.

All the Best!

Boot the laptop, and immediately after you see the DELL splash screen, start pressing F8. This will display a startup menu with a few different options. Choose the option that says "Last Known Good Configuration" - this will back out the last update changes that may have caused your problems. Good luck!!

Looks like you've had a bad day with computers! Let's see if we can take some of this on today...

On the first laptop (these ideas may work for both, but I'll address them the way I would my own, and we'll go from there), it looks like there is too much stuff being loaded into memory during system startup. This is not uncommon, particularly in computers which have teenagers as primary users.

I would restart the computer, and after the manufacturer's splash screen and before the Windows splash screen, hit the F8 key on your keyboard. This should bring you to a startup menu, which will be a black screen with white writing on it. You will be able to make your choice by moving up and down with the arrow keys on your keyboard. Choose SAFE MODE and hit enter.

If you do not see this screen, then you did not time the hitting of F8 corectly. You'll have to restart and try again.

Once in safe mode, click Start, then RUN. With Run open, type this command MSCONFIG and hit enter.

The next screen that opens is the configuration utility, which allows you to change the things that start with your computer. The last tab on the top should be STARTUP. click this.

Because we are shooting in the dark here, and we are not sure what is stopping the startup process, in the lower right corner of the window is a button that says Disable All. Choose this and click APPLY.

When the mouse comes back, click the next tab, which says SERVICES. Under the first window, you will see a small check box next to a line that says Hide All Microsoft Services. Place a checkmark here.

Again, in the lower right corner, click Disable All. Then click OK. When asked to restart, chose yes. This time the computer should start normally.

Now, this should start your pc, but you still have trouble with no AntiVirus software on your computer. The programs are there, they are just turned off. You'll have to open the program from the program files list, and enable it once again.

I'll comment on the other one after I eat dinner with my family.....

Hi,
boot it, as it starts, keep tapping the F8 key,
should take you to, system startup utility,
take the top option
" last known good"
let it do it's thing
Reboot.

hope this helps
Regards
Richard.

Software issue or error
Errors generated by software programs can cause a computer to reboot unexpectedly or without warning. If you are running Windows XP see the below section "For Windows XP users" before continuing. If you are not running Windows XP or following the below steps still cause your computer to reboot without warning. Boot your computer into Safe Mode, and let the computer run in Safe Mode.

If the computer is still rebooting in Safe Mode the issue is likely not software related but something else, skip to the next section. If the computer is not rebooting in Safe Mode it is likely you have software related issue. We would recommend you run through the basic troubleshooting section for your operating system.
For Windows XP users
Windows XP is designed to automatically reboot each time an error occurs such as a BSoD. Although this may be nice for errors that do not occur often, users who have a re-occurring error may wish to identify the error to troubleshoot it. Below are the steps on how this feature can be disabled and enabled in Windows XP.
From the desktop right-click on My Computer.
Click the Properties option.
In the System Properties window click the Advanced tab.
In Advanced click the Settings button under Startup and Recovery.
In the Startup and Recovery window uncheck the Automatically restart check box.
Click Ok.
Now if the computer generates and error it should not automatically restart and enable you to display any errors your computer may be experiencing.
Hardware issue or error
Any failing hardware component in your computer could cause your computer to unexpectedly generate an error and/or reboot without warning. If you have recently attempted to add a new hardware device, remove that device to make sure it is not causing your issues.
Make sure you are not encountering any hardware conflicts by viewing Device Manager for errors.

New drivers can also cause this issue, if you have recently performed any hardware driver updates you may wish to try an earlier version of the drivers.

If you have updated drivers and removed any hardware that could be causing this issue and continue to experience random reboots, it's possible that the memory is bad in the computer.

Finally, hardware devices that are not installed properly in the computer can also cause random reboots. Make sure all the cables and expansion cards are connected properly to the computer. The best way to determine this is to disconnect and reconnect all cables and expansion cards.
Computer virus
Computer viruses such as the blaster virus are written to reboot your computer without warning. Usually these viruses will make the computer reboot ever 5, 10, 15 or 30 minutes after the computer has booted.
If you believe your computer may be infected with a virus or are uncertain if your computer is infected with a virus make sure your virus scanner definitions are up to date.

Heat related issue
Many computer today are designed to turn off or automatically reboot if the computer, processor, or other device in your computer gets to hot. If you have heard any abnormal noises coming from your computer recently such as a high squealing this could indicate a fan may be failing in your computer.
You can first start by verifying the fan on the power supply is working by examining the back of the computer and seeing if the fan is moving and moving smoothly. For all other fans in the computer you will need to either open the computer and make sure the fan are working (processor fan and case fan) and/or if your BIOS monitors the RPM of the fans enter BIOS and make sure the BIOS does not report any errors.
Users may also be able to determine how hot their computer is by onboard thermal sensors, if your computer comes equipped with these sensors make sure your CPU is not running to hot.
Issue with operating system
If after following each of the above recommendations your computer still continues to reboot it is likely that you are experiencing a Microsoft Windows operating system related issue that cannot be explained. To help make sure this is the case please try the below steps.
Reboot the computer and enter CMOS setup as the computer is booting.
After you have loaded the computer in CMOS setup let the computer sit.
If the computer does not reboot while letting the computer sit in CMOS it is likely that you are in fact experiencing an issue with Microsoft Windows and it is recommend that if you have followed all of the above recommendations that you reinstall your version of Microsoft Windows.

This issue could be caused by any of the below possibilities

Software issue or error.
Hardware issue or error.
Heat related issue.
Computer virus.
Issue with operating system.


Software issue or error

Errors generated by software programs can cause a computer to reboot unexpectedly or without warning. If you are running Windows XP see the below section "For Windows XP users" before continuing.
If you are not running Windows XP or following the below steps still cause your computer to reboot without warning. Boot your computer into Safe Mode, and let the computer run in Safe Mode.

If the computer is still rebooting in Safe Mode the issue is likely not software related but something else, skip to the next section. If the computer is not rebooting in Safe Mode it is likely you have software related issue. We would recommend you run through the basic troubleshooting section for your operating system.

For Windows XP users
Windows XP is designed to automatically reboot each time an error occurs such as a BSoD. Although this may be nice for errors that do not occur often, users who have a re-occurring error may wish to identify the error to troubleshoot it. Below are the steps on how this feature can be disabled and enabled in Windows XP.
From the desktop right-click on My Computer.
Click the Properties option.
In the System Properties window click the Advanced tab.
In Advanced click the Settings button under Startup and Recovery.
In the Startup and Recovery window uncheck the Automatically restart check box.
Click Ok.
Now if the computer generates and error it should not automatically restart and enable you to display any errors your computer may be experiencing.

Hardware issue or error
Any failing hardware component in your computer could cause your computer to unexpectedly generate an error and/or reboot without warning. If you have recently attempted to add a new hardware device, remove that device to make sure it is not causing your issues.
Make sure you are not encountering any hardware conflicts by viewing Device Manager for errors.

New drivers can also cause this issue, if you have recently performed any hardware driver updates you may wish to try an earlier version of the drivers.

If you have updated drivers and removed any hardware that could be causing this issue and continue to experience random reboots, it's possible that the memory is bad in the computer.

Finally, hardware devices that are not installed properly in the computer can also cause random reboots. Make sure all the cables and expansion cards are connected properly to the computer. The best way to determine this is to disconnect and reconnect all cables and expansion cards.

Computer virus
Computer viruses such as the blaster virus are written to reboot your computer without warning. Usually these viruses will make the computer reboot ever 5, 10, 15 or 30 minutes after the computer has booted.
If you believe your computer may be infected with a virus or are uncertain if your computer is infected with a virus make sure your virus scanner definitions are up to date.

Heat related issue
Many computer today are designed to turn off or automatically reboot if the computer, processor, or other device in your computer gets to hot. If you have heard any abnormal noises coming from your computer recently such as a high squealing this could indicate a fan may be failing in your computer.
You can first start by verifying the fan on the power supply is working by examining the back of the computer and seeing if the fan is moving and moving smoothly. For all other fans in the computer you will need to either open the computer and make sure the fan are working (processor fan and case fan) and/or if your BIOS monitors the RPM of the fans enter BIOS and make sure the BIOS does not report any errors.
Users may also be able to determine how hot their computer is by onboard thermal sensors, if your computer comes equipped with these sensors make sure your CPU is not running to hot.

Issue with operating system
If after following each of the above recommendations your computer still continues to reboot it is likely that you are experiencing a Microsoft Windows operating system related issue that cannot be explained. To help make sure this is the case please try the below steps.
Reboot the computer and enter CMOS setup as the computer is booting.
After you have loaded the computer in CMOS setup let the computer sit.
If the computer does not reboot while letting the computer sit in CMOS it is likely that you are in fact experiencing an issue with Microsoft Windows and it is recommend that if you have followed all of the above recommendations that you reinstall your version of Microsoft Windows.