Aight to get to the BIOS or 'setup' screen it just depends on the mother board and the BIOS that you are running for the key you need to press...

Common Keys are the DEL key and the first 4 F# buttons and also F7 & F8 then you will need to fumble around in there til you find a clock of some sort. It should be in the general area...if that is also fast you might want to try changing the CMOS battery...

Windows relys on your BIOS clock to give you the time on the Windows clock. If changing the CMOS battery doesnt work then you motherboard is starting to go wacko on ya...

Also be of warn, taking the CMOS battery out will reset your BIOS\CMOS settings to default so if you have any custom settings in there make sure to write them down or make sure you remember...