Now when I say it worked okay, I mean after the driver conflict I had to reset the machine a few times, and as such it started to develop a habbit of only actually doing anything about 1 in every 4 times. I mean, the BIOS did not even start or anything, rather the monitor reported 'no signal' and went to standby. When it eventually did do something the BIOS would report either 'BIOS checksum wrong' or 'BIOS is bad', in either cases I had to change the settings before boot. So by going back to a previous version of the BIOS it worked for a week.
Now the problem has come back and it is worse. It just froze and then I pressed reset and nothing - just 'no signal' reported. Occasionally now (1 in every 10) times the BIOS will start, report that it the settings need changing and then it tries to boot into XP. After the green bars get to about their 3'rd appearance they just stop and the system hangs. I did just get it to boot into safe mode, but that was after the 4th try, and nothing since.
If anyone has any ideas or advice they would be gratefully appreciated.