[help]-strange problem loading new programs

[FETUS]

My searches didn't turn up anything on this so I hope someone knows my problem.

I'm running Windows xp home sp2 on an amd ath 2100+ with 512mb of ram if that's helpfull.

Recently I haven't been able to load new programs especially installs. I'll try to ren the exe and get an error restart and it will run fine. That is just a big hastle that I don't want to deal with. Anybody know what the problem is and how to fix it? Please before you tell me I need to format that would mean a wasted weekend(maybe longer) just installing all the programs I need for work and a good afternoon installing all the programs I want for play.