I see what you're saying bsod. There is a stickers on the front of the case from the manufacturer that states 256MB is the max. That's what I thought the problem was when I had 320MB in there, but as I say, it still failed to boot with the single stick of 256MB.
It boots fine with just the 64MB and I can then access the BIOS so I'll see if I can increase the fsb in there. No manual I'm afraid - sourced from PC World and they didn't issue one aparently. I'll hunt about on the web for one. Trouble is I can't see who the manufacturer of the mobo is.
If you're limited then by the amount of RAM per slot and it's only happy with 64MB, the mobo only has two slots on it, so the max I could use is 128MB. Is this enough for XP to run on happily?