It's a long shot but you could try taking out your memory card(s) ...then putting them back in.....and boot up.
if it does not work, then try resetting the Cmos by taking out the small battery that sits next to your memory cards.
But remember to unplug your comp. 1st before doing this....Tkae it out & leave it out for bout 5 minutes.
then put it back in, plug back in the cord & bootup.
if that still don't work then, move over the jumper on the Cmos....next to where the battery was.
there should be a 3-prong jumper.....move it over to the other side, and bootup the comp.
if it works, it should say that the Cmos has been reset successfully ....then shutdown, go back inside & move the jumper back over to the original side it was on.
that should do it......also make shure you un-plug the comp. if your moving the jumper over.