I have a compaq persario laptop computer that i have had for about 6 years, i am running windows xp home. this problem has just recently started....sometimes when i power the laptop on i get nothing but a black screen...led lights go on and i hear the hard drive spin, other times i can boot all the way into windowsa then after a few min the computer shuts down then try to power back up get nothing but black screen again......after powering on a few times it starts fine again.........could this problem be a bad or going bad cmos battery?? thanks or any other ideas??