This is pretty much a tech question, not so much a web design question, so I'll include a tip at the end, just to be sure. I have an IBM Thinkpad that has a dead CMOS battery. Now, I understand that a bad CMOS battery would prevent the correct time from showing, but would it prevent the entire notebook from booting up? Yes. The time issue gives you an indication that the battery is giving up' the Battery being dead will not supply current to fire the CMOS chip or perform the power on self test/POST. This is where the beep codes are helpful. In extreme cases '6-mos-year' the CMOS will Erase itself.