yeah, try setting values in your bios to it's appropriate settings - save the settings and exit - power off your computer wait for 30minutes or so.
When you power back up go into bios and see if the settings and CMOS date/time is correct. Most notably if you have any year other than 2003/2004 for your CMOS date/time then you have a flat battery.
Otherwise, you should consider the second suggestion that you have an aging power supply.
A fine day!