Desktop keeps rebooting, not the system, just the desktop

Chances are it's OS or hard drive corruption. You may need to reload. If you haven't backed up your data, I would suggest doing so now.

Does it Boot or is it stuck in a boot loop cycle? Have you done ANY hardware or software, new OS?, updates/upgrades lately? Memory? Put in a new CMOS battery. Try reseating Memory Mods. Are the Fans, heatsink, vents clean? Open the BIOS setup, check Clock, set if necessary, Disable Auto Reboot. Remove ALL Media DVD,CD,USB devices, Printer cable, ect., Will it boot to Safe Mode? Take a look : http://searchenterprisedesktop.techtarget.com/Steps-for-solving-the-reboot-loop-problem May be a bad HDD? Remove and test, replace if necessary.

Try in safe mode. When won't works, the os files are corrupted and maybe the hard drive too.

you will need a Windows boot disk / Windows install disk / WinXP disk to reboot the PC and install / or repair your OS

rescue disk will not boot your PC
to enable that you need to enter the BIOS, press F1, F2 or Del to enter BIOS , then you need to look for the BOOT seq in BIOS, change that to CD DVD drive as the 1st boot device, Save and Exit and insert the boot CD and restart
this should give you the solution

You could have a few different issues.

1. You have a driver issue. Try running windows repair from Microsoft install disk.
2. Possible power supply issue.
3. Bad hard drive. Possible bad sectors. Nothing to do here but replace hard drive.

Try disconnecting all hardware in system except hard drive and video card. This will include network cards and any other peripherals. Try to boot up.

Try to boot into vista's safe mode, this can usually be done by pressing F8 after POST, but before you see the vista loading screen.

Once in safe mode go to:

Start > Control Panel > System

on the left you will see " Advanced System Settings " Click that

a new window will pop up with your system properties, click the " settings " button near " startup and recovery "

Make sure the little check-mark near " restart automaticly " is NOT check, then apply, and OK out of all screeens and reboot the system. If the problem persist, you may need to insert the Vista disk into your system, and do a recovery, or restore.

it does sound like a boot virus problem. you need to boot into system restore. to boot from the restore partition you need to switch on your pc and repeatedly press either F10, F11, Alt+F10, or Alt+F11. you do this until you see the system restore starts. you will be able to fix windows, or you can do a desturctive restore and restore your pc back to factory settings, but you'll loose your photos and anything saved on the hard drive.

go on BIOS setting and change the booting device sequence. system hard drive make it first in booting sequence.

press ctrl+alt+del

then in the task manager click shutdown

To get to bios settings its usually the key DEL wen it first boots up.
once there there will be a Restore default settings and then hit y then save and exit.