I wouldn't go as far as a full nuke... Well I probably would! But it's not necessary, you could just give it a cleanup.
Run 'MSCONFIG' & clean up the startup section so it's only got things that you need starting, that'll free up your computer & speed up it's boot time.
Give it a quick malware/spyware check to make sure none of that's getting in the way & ensure your drivers are up to date.
It still confuses me how slow it's running for you, I can get the same fps on a p3 700 & that's a shockingly slow cpu.