well, it'd have been better with two dimms for it to take advantage of DualChannel memory. It's unusual for a PC to be equiped with only 1 Dimm when it's capable of DualChannel.
Perhaps that is also the problem. This means your only getting the memory throughput of 533MHz instead of a possible 800MHz (or if it was run in dual channel 533MHz, 1066MHz). And ontop of that, because it's nowhere near in sync with the FSB, it's more inefficient.
I dunno what to recommend. Just to see if it has an effect, changed the Memory FSB down to 400MHz. I'm not expecting it to do much, but you never know.
Delta: "What's wrong Chris?? Chris: "I miss my old Cyrix"