Dustket

I own a Dell Dimension 8400 with a Pentium 4 3.0ghz processor. 775 socket i think it is. my problem is anytime i use a program my cpu's fan blows hard...very hard. It almost sounds like a jet. from what ive found out on the dell forums is that the heatsink dell first used was defective. Well my comp is old and not under warrenty. I talked it over with a guy at work and he said i should try some silver thermal compound. I did and the fan blows insanely loud still.I contacted dell and they treated my like a moron so im done with them. Heres my question. Do any of you guys know of a heatsink or heatsink/fan combo that would be a direct replacement as far as being able to ues the clips that Dell uses to hold the heatsink. Also the heatsink does not have a fan. it uses ducting to pull air thru it. but a heatsink with a fan would be nice. thanks guys.