TuneUp Utilities 2010 Registry Defrag black screen?

Ok, I ran the TuneUp Utilities 2010 registry defrag on my dads computer, and it needed to optimize. I try to restart the computer afterwards, but all I get is the white flashing underscore, after the Acer logo where it tells you to press F2 to access setup (BIOS Settings). I am not sure why it is not restarting, but I think it is because the defrag messed it up? I may need to install a different operating system, but as of now, I think that may be my only option. Please help