Computer help

[hotreds]

System is XP. I noticed recently that several programs won't load. One freezes at the initial screen, two others tell me the encountered problems and need to close. I've tried deleting and re-installing, but then I come up with a Windows installer error. So, I followed the advice online from Microsoft and unistalled that, and reinstalled the new version. No luck. I also restored my computer to a previous time w/o and luck. I also emptied my cache, temp files, temp internet files, etc etc. I'm a bit hesitant to use any register repair programs(if that is, in fact, the problem), but maybe one would help.

Any experts out there have any ideas? No, I don't want to re-install XP!