Best I ever did with a Duron was a 600MHz model I up-clocked to 1.1GHz at 133MHz FSB (air-cooled, Alpha PAL heatsink). The same chip would also go to 1GHz at 100MHz, which was quite a bit harder on it as the clock multiplier was a lot higher.
I do think someone did have a good movie of frying an Athlon or Duron at one time, but that one's a fake.
Intel Q9450 @3.2GHz, Gigabyte GA EP45-UD3P, 4 x 2GB G.Skill @4-4-4-12
Antec P160SW case (modded), Xigmatek 750w PSU
3x 500GB (RAID-5), , OptiArc 7200S, ASUS E818A3T
Creative X-Fi XtremeGamer, Hauppauge HVR-1800, Radeon 4890