Blah, don't forget to lock the AGP/PCI frenquency to 66/33MHz, otherwise it will increase along with the FSB's, and you might get your data corrupted (as IDE frequency depends on PCI's)...
Second thing, to know if an o/c is really stable, just booting windows and messenger isn't enough. You should "burn" (load the CPU with heavy tasks to test its stability) the CPU with a software like SuperPI or OCCT (or CPU Burn, etc.).
Third thing, a fan is a thing, a heatsink is another
(even if you put a fan on a heatsink, haha), but yeah, avoid overheating you CPU. (use monitoring software such as Motherboard Monitor, Everest, Speedfan, etc.) An "acceptable" CPU temperature under full load would be around 60 to 70°C (less is better).
/ 
