roll back software

I am looking for a FREE replacement for XP SYSTEM RESTORE. I have been using COMODO TIME MACHINE which is similar. My issue is that for ONE of my DELL DIMENSION 8100s seems to have an issue either with the program or the file or the site(s). After I loaded it, last of course, it asks for a restart. When I do so I get a "DISC ERROR READ" screen every time. It does not matter from which site I download it from. Under those conditions the only way to reboot is to reload the OS, XP PRO. I have done this 3 times on the same tower using the same hdd and another hdd. Nothing seems to avoid this issue. THAT tower now has ONLY XP SR, no additional backup program. I CANNOT find ANY FREE similar program. The closet I have come across is EASAFIX trial, ROLL BACK RX, paid, PC TIME MACHINE, non existant, and WONDER TIME MACHINE, shareware. Any alternatives? The other 2 81s do not have this issue. THAT 81 runs fine without CTM. SR does not always work and reloading the OS at those times is time consuming as all data is lost. Under those conditions, would a REPAIR installation be what I should do? Or should I access ASR? How do I use it? All info welcome.