Checksum error?
Do you remember what the message it gave to you was?
(I dont recall checksums being caused by fans.... just CMOS Data, which brings my next great clonfusion:
Have you tried resetting the CMOS?
(Power off the PC (duh), unplug it, Remove the CMOS battery for 10 >minutes< and then reinsert, and plug everything back in, and restart)