I got it to work in the end.

I unplugged all usb devices from the pc except the monitor keyboard and mouse. I removed the 2nd monitor(I think this was probably the problem but not certain), my printer, the usb modem and my external optical drive.
When I restarted the computer and selected vista from the boot options it started up ok.
re-conected everything and windows seemed to get it all to work ok. Had to reinstal thomson modem drivers from the disk.

Gave vista a bit of a workout last night, ran a few programs at once which which would have made xp start to struggle but vista managed good. Had it on for 24 hours without a crash.

Impressed