before anyone else harps on about overheating I have reset the machine after it has been running for 7 hours and as it rebooted I intercepted the bios and checked the status of stuff. The CPU temperature is reporting just 31 deg C. IT IS NOT OVERHEATING!!!!!
Meanwhile, when the mouse goes slow so does everything else. The whole thing just grinds to a halt, you can't do anything, not even bring the task manager to the front. The clock stops, music glitches and eventually stops repeating the last second it plays. Everything sticks. Generally it will reboot itself but one time it just sat there for nearly an hour, the clock in the toolbar was stuck at the time it slowed down.
Rans6.....