XP disk reboot & ms update conflict

hi, i am not very experienced w/computers. i recently reinstalled disks to restore factory settings. i am original owner of emachines MT1440, w/XP home edition (2001). 1.4 ghz. and 128 mb ram. not very large capacity but it has always worked fine for my personal use.

upon reinstall, i sought to apply the patches to protect computer, part of this was the (what i think is ) the relatively new windows authenticity verification. seemed to go through okay, i applied the service pack 2.

the problem i have is that soon after during regular use, the mouse and keyboard will lock up, also it reboots itself (these seem to be two separate issues - i don't know). when attempt to restart the computer in safe mode i was getting a window that basically said that couldn't log on to user profile as part of the reg was missing, upon clicking would have the basic startup screen, then the mouse will disappear, and or sometimes the computer will shut itself off.

due to this problem i have tried to reinstall the disks several times. i am not able to use this computer for this question, but it is currently up and running i have not installed any updates or linked to internet with it.

is this fixable or do i have to write it off? i really can't be without a computer as i do some contract work from the home.

your assistance is appreciated.