huh? its not a laptop? probably not (7200 rpm hd) well:
I had a similar problem with my old laptop which hanged completly because of my ram was toast (same thing happened, lights blinking and all

!
For the light thats blinking check you manual and se what it means. It might be a hardware issue, at least that was the case for me.
Of course I should have started out by askin or assuming: does this happen in Xp?
cheers, Klod