Last night I tried to crank my 300 (100*3.0) to 350 (100*3.5). Windows 98 did not come up (some error, GPF?). I reset the core clock multiplier back to 3.0, and it came right back up (whew!). Could this be caused by heat? I didn't modify my heatsink/fan (I heard it should handle at least up to 350). Also, I did not change my core voltage (left it at 2.2V) should I try 2.3V?