Right, so I managed to make a 64 bit flash boot disk whilst in vista and xp. You do have to download the 32 bit bootsect.exe file from somewhere. I then used this tutorial.
The flash disk worked fine, booted up and started installing. However, it still crashes at between 25-40 % on 'expanding windows files'. The difference is that it never hangs, just reboots. I tried it in safe mode, it hangs whilst loading the disk.sys driver
for a few seconds, but i'm not sure if this is normal. It also managed to get a little further (around 50%) before rebooting.
I also tried installing to an ide hd rather than a sata one, and again this seems to get slightly further.
Could it be the PSU? It's a fairly cheap 500w one that worked fine in my old computer, but I'm thinking that maybe the new cpu, more memory and a better mobo are pushing it over the edge. Might also explain why it lasts longer installing from a usb flash disk rather than a dvd drive (less power?).
Any ideas would be gratefully received!