I've run into this problem before with my 17" MAG Innovision flat panel monitor; it won't show BIOS screens(or splash screens, I forget the technical name for them). For example; the "media test" ...
When I sit Idle in BIOS and monitor the temp on my ABIT KT7A/700mhz Duron, the idle temp is about 49.5C, but when I go into windows and fire up my VIA hardware monitor, I get about 34C idle temp.