If you can start your PC any time now, turn it off, disconnect power cable, press and hold power button for at least 20 seconds, next open your PC, look for a shinny round object on your motherboard, it is CMOS battery, note how it is placed, remove it for at least 30 minutes, once removed, press and hold power button for 20 seconds, put everything back together, use your best working technique to start a PC, any errors?
I would actually recommend to purchase new battery, if you still have an original one, it is not expensive, RadioShack has it.