Cheers. I'm in Ireland, though postage is much the same.
I think it takes all Dothan Pentium M's 400/533. Memory speed and Front side bus are 400 MHz but (I think) it can run the CPU at 533. It has the 915GM chipset, and I remember when I maxed the RAM DDR2 to 2GB, that it was a quirk of this machine that Dell set it up that it would run ram asynchronously at 400 with a 533 processor. I'm not 100% certain though.
It was a basic machine when new. I'm not expecting miracles. I thought it might give a little boost, and perhaps a tiny bit more battery life. People are junking old CPU's even old machines as worthless, old P4's etc. My FIL was using a P4 1.7 desktop, with 1.25MB RAM with USB1 and a CDROM and it was killing me to support it. So slow, especially for anything connected via USB. I picked up a 3GHz, desktop machine with 2GB, and USB 2 and a DVD/CDRW for a very little, and its vast improvement. Now usable for everyday things, like web, skype, the odd doc. Which is all he does.
I'm trying to resist upgrading another old P4 1.7 at the moment. The cost of RAM on these old machines makes it pointless usually.