Thank you very much for the quick reply guys.
Barman58, I'm not sure I know which driver it is that controls the fan? I have used some of the old drivers for some of the hardware and that has worked out.
Nikolay, I left the system on to transfer 100GB's of data, do a virus scan and to let a few other programs do long tasks.
Frostmourne, no longer under warranty because of the Windows 7 upgrade. Also I was under the impression that the fan is controlled by the Bios and as far as I know, there have been no changes to my Bios.