My computer won't boot - HP Media Center m7250n (ED842AA) PC Desktop

Unplug the computer, Hold down the power button for 5 seconds.
Plug the computer in. Power on the computer.
Call, text or email Shane 801.554.4142 / [email protected]

Computer does not boot up The problem maybe the RAM, it is faulty or just needs reseating to make proper electrical contact.
Reseat the RAM and then boot up your laptop. If it still does not boot up then remove the RAM module/s and take them to your friendly computer repair shop and get them to test the RAM for you. Just like you sometimes need a mechanic to repair your car, sometimes you do need a technician to diagnose and identify the fault or faults on your computer. Not only does a good service technican have the experience to deal with this type of problem, they also have the equipment that allows them to look at things the average computer user can't see, and he has a collection of replacement parts that can be used to quickly test individual components on your computer.

If you want to keep your important data, use some softwares can solve thewindows won't startproblem most quickly, and no data will lose. Besides, it is very easy, even the people who lack of computer knowledge can deal with windows won't boot issue.

Turn on, hold F8 button down until boot menu appears. Download Norton Boot Recovry to disc from another computer. Install in ur CD/DVD drive. Boot ur computer. Or install ur operating system disc in cCD rom drive. Reboot computer, hold F2 button down, modify BIOS boot sequence so CD Rom in 1st boot device. Boot computer, repair or reinstall operating system.

Try checking the CMOS battery

Somehow your MBR (Master Boot Record) likely got corrupted or possibly your hard drive went bad coincidentally.

Simply, you will start your computer from your Windows CD/DVD install disk, then when at a DOS prompt ( D:\ ) you will then type: FDISK /MBR (press enter).

Find your Operating System install DVD and start your computer with it, then follow instructions within this discussion:
Restore Windows XP MBR without Windows XP disc

Alternatively, review my search results for other instructions:
fdisk mbr windows xp Google Search

Windows won't start up? Well, try this Download Tenorshare Data Recovery from its offical site and install it. Burn it into CD/DVD, or USB flash, put into the computer you need to repair, Bios setting. It can make sure your important data will not lose. Best of luck
Related: windows won't start

reinstall XP or upgrade to Windows7

First you should check if there is any disk on your cd room, if there is any disk you should remove the disk from the cd room, if there is no disk the possibility is your hard drive getting error
Press f2 or delete to enter your bios set up system
Look for boot menu
Set the first boot as a HDD and the second boot as cd room and disable the third boot
Save and Exit the setting
if your computer still won't load you need to reinstall your windows
insert windows cd and go to set up again by pressing f2 or delete button
Set the first boot as cd room then the second boot as HDD
Save and exit the setting again
When the message press any key to boot from cd appears you should press the space bar or another key
Then just follow the instruction of formatting

Depends on what you mean by won't boot from DVD or Hard Drive,
it sounds like your boot order is what you're looking for help for.

To do this you need to get into your computers BIOS (or "Setup")
You can do this by rebooting the computer and the very very very first screen you see tells you how,
usually by pressing DEL or F2 or F10.

Without knowing the specific computer you're looking for help on I can only point you in the right direction however keep in mind the BIOS is for advanced users only and you can damage your computer by randomly changing settings.

What you're looking for though is usually called the Boot Order or Boot Sequence
You'll need to set whatever device you want to boot from higher on the list (usually with the up arrow or PgUp)
If you don't see your device on the boot list then it may not be detected due to failure.