No need to be sorry
Unplug the computer.
Open the case.
Remove the little lithium battery (it looks like a silver coin) on the motherboard.
Put the battery back in after a couple of minutes and turn the computer on. When the computer boots you will get a "checksum error" message - enter BIOS and load default settings (or something similar).
Don't forget to save before you exit BIOS.
And - please - when you have the case open: Have a look at the label on the PSU.