|Probably 1 of 2 things....bad ram module or corrupt start up files. If you download memtest86 and make a bootable cd.....then boot to the cd on startup....this will test the ram modules. See if it will load into safe mode with networking, if it does try downloading and running malwarebytes or superanitspyware. Perhaps a nasty is causing this. If you cannot get into safe mode or virus removal fails you may have to stick in the xp disk and do what is called a "repair". You boot off the xp disk and hit enter to install xp (don't select the recovery console option).......it copies over a bunch files and then it will search the hard drive for currently installed operating systems...hopefully you can see your xp installation (proabably on c:\), so hightlight your operating system....and choose "R" for the repair option. It will reinstall windows, but you will not lose any of your stuff. If the windows installation does not find the old windows install, or you do not get the repair option then (f3) to quit and you're no worse off. At that point it may be a nasty which has corrupted the file system itself.....So you boot again to the windows install cd and pick the recovery console option, it will take you to a few dos prompts.....just pick your windows install and hit enter to the questions.....should leave you in a black command prompt box with a c:> prompt type in chkdsk /r hit enter and let this try and repair the file system, could take awhile. If it finds and fixes the errors......go back now and try the repair installation again...hopefully you would see the old install and get the repair option. I'm sure others will have suggestions as well. Can be a challenge, and you do need the xp disk with a serial number key.|
Goodluck. Another way to test the ram depends if you have 2 ram modules; you could remove one, see if the computer boots normally, if not take that one out put the other back in, test again. If you have only 1 ram module you need memtest.
Ps. if you leave the xp disk in the cd when it reboots (its a bootable disk) it will try to boot off the cd first and then if you DON'T press on any keys it continues on with the hard drive and the installation....some folks get caught in the loop because they hit a key when it restarts which begins the install again.....so the only time you the "any key" to boot from the xp disk is the very first time...if the computer restarts during the install do not hit any key to boot the cd.