I have a 167Mhz Pentium with no fan, just sink

. Runs fine, but thats as high as I'd take it. I'm not taking the fans out of my 2000 though, stupid vacuum cleaner it is.
I have seen really really big +$$ heatsinks for fast new computers, but they look like copper sculptures, sorta ridiculous, but viable if you got a foot all round your processor.