Ok snow,
First try, got as far as loading Xp then restarted, same on next run through. Third time gets to windows, where I managed to login.
When logged in I had the classic start menu displayed (normally have xp one) and in settings Xp menu was still selected. Before I could check anything else it rebooted again, getting through to Windows loading before another reboot.
In bios I can find no mention of the ram (tried every option, maybe I'm missing it in an obvious spot).
No bios beeps on start up or at any other point.
Other info that might be helpful:
400 psu
pny geforce 6200 agp graphics card (newly installed and can run quite hot).
Any other info needed I'll find it out, any more ideas?
Thanks
David