My dell laptop keeps going back and forth from the loading logo screen to black screen

Your monitor display settings are no longer set (synced) with the upgrade. Boot into Safe Mode by pressing F8 during boot and lower the screen resolution.

You will have to check Display drivers in Device Manager, and make sure they are loaded.

perhaps you need to reinstall the operating system,the system files might be corrupted because of power problem,and there's "windows loading files" thing,so the windows cannot go further because it cannot find some files while loading. do you need any help with installing operating system?

start tapping f8 after you boot the machine, when given the boot menu, try to load safe mode, and see if it loads. if it does, then you need to do a system restore back to before you got the black screen. more than likely windows loaded an updated driver that disagrees with your system. try that and let me know what happens :)

If you need further help, reach me via phone at https://www.6ya.com/expert/joel_63c670a84e9f6a97

only way to bypass this is use a recovery disk to boot from and then perhaps the issue will manifest itself

otherwise, it's the dreaded re format step

load dell diagnostics and check your hard drive, one of the options when the dell logo is on the screen.

this is often related to a possible motherboard problem. Try these steps: turn it off, remove the battery, and AC adapter, then press and hold the power button for about 5 to 10 seconds. Once done, reconnect at least the adapter , turn on the laptop and as soon as the Dell logo shows up, tap F2 a few times to enter System Setup (BIOS screen). From there, go to the Maintenance category, and select Load Defaults, press Enter. Press ESC, then select Save/Exit, restart the computer and see how it goes.

Immediately after seeing the Dell logo, keep tapping the 'F8' key,
until you see a "menu" (white text over a black background)
giving "startup" options for Windows XP.

Select "Safe Mode" and see if you can start in that mode.
Then, use "System Restore" to go "back" in time, to the most-recent checkpoint (date/time) where your computer _DID_ work.

Restore to that point, and restart.

Boot from your Vista CD, and click next and Click Repair. Select the options that best suit you.

First, I want to know if you sees the Dell logo after turning on the laptop? If yes then this is no boot issue.
1. Immediately run the PSA. Make sure laptop is off. Press and hold down the Fn key, while holding down Fn key press the power button at the same time just once. Once the Dell screen loaded you can now let go of the Fn key. Check if the PSA will run short test for the LCD, RAM and HDD. When full color displays on the screen just press Y. PSA will continue. Just take note of any error code will appear on the screen such as 0141, 0142 and 0146 these are HDD failure errors which means HDD needs replacement. If the test says no errors found then proceed to step 2;
2. Try restarting the laptop once you see dell logo then keep tapping F8. Select last known good configuration. Press enter key. Just wait and check if laptop will load Windows. If not then, restart laptop keep tapping F8 try to select safe mode check if it will load Windows. If not then prepare the Windows OS disc the one came with your laptop.
3. While laptop is on insert the Windows OS disc. Restart the computer. On the Dell screen keep tapping on F12 to show boot menu. In the boot menu select CD/DVD ROM Drive. Press enter then keep tapping on space bar until it will say Windows loading files, please wait.
4. In the User Interface it will show you some options to select. Once the Install screen comes up look on the lower part select Repair Your Computer. If will ask you to do Startup Repair, please do start up repair. If fails try the System Restore. If fails then step 5;
5. If you have important files in your HDD then back up your files first. After backing up of files you can now install the Windows OS. Here is the process in installing the Windows OS. Insert the Windows OS disc, restart the laptop, keep tapping F12 on Dell screen, on boot menu select CD/DVD ROM Drive.Install the Windows OS. Just complete the installation.After the installation install the laptop drivers.

plz try to boot through safe mode, if you can then log in normally.
if you cant boot from safe mode then you have to reload or repair your os.