your set up is almost the same with me XL, i have p3-800E now and run at 1000 mhz, the problem just 41 pci bus speed but i run this setting for 3 month already! and nothing crash problem yet

and my p3-800 can boot at 1066 (133fsb) but it's just stable in the desktop like: play irc, surfing etc and i got freeze when i play a game!
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p3-800@1000 1.75 alpha pal35t
asus cusl2 1001.a
320 sdram pc133
asus v7700