Search Bug Under Winxp Sp1 im in trouble... any ideas on this?

[finaldesign 0]

Ok,here's the deal. Every time when I try to make a search if it's set to search on mycomputer, or only C:\ disk, after few secund of searching it crashes coputer, causing a massive processor & memory usage, and simply halts and block the whole system. then i must reboot.I'm suspecting it's a virus maybe, but sophos v.3.87 founds nothing.Any ideas on how to solve that? Btw. it's my computer from work, it has been about 2 years from last reinstall of winxp. I'm starting to believe that winxp can degrade itself after few years...