Today I cleaned up my case and rear fan and cpu fan and the gunk in the heatsink fins, after removing the heatsink fan. I used a vacuum cleaner with a soft attachment and about a dozen Q- tips. I do this about once every 6 months. This is the second time on this machine which is nearly 12 months old. It is a Chaintech VFN4 in an Antec 1050B mid-tower, AMD64 3500+.
And each time I do this, I have to reset the BIOS settings for date and time, disable C&Q, and disable the fan control, reset shutdown temps, and other things.
I thought the function of the CMOS battery was to keep these settings. According to Everest Ultimate edition, VBAT Battery is reading @2.64 volts, therfore I assume the CMOS battery is working.
I've had many computers, but I've never encountered the loss of BIOS settings merely by unplugging the computer.
I have the latest BIOS available on the Chaintech site.