what mobo are you running?
You would have to change some sort of memory multiplyer (that is, if you dont want to change cpu speed too)
on most Abit motherobards they have a divider of fsb/memory,
like if the fsb is at 133, and the divider at 3/3, then the memroy would run at 266mhz (133/133, then x2 because of DDR, of course.)
166 at 3/3 = 333
133 at 3/4 = (400?)
anyways search in your bios for something like that.
You're the guy from that hamburger train, right?