I have to support 11 Gateway Pentium D computers in my video lab, running XP Pro with 2 GB of RAM. Suddenly, 2 of the machines will not boot. Really won't boot, as in the DVD drive light briefly flashes at startup, but the hard drive never spins up. I don't even get the boot menu/bios screen. I've tried the basics, nothing seems to work. I'm not a newbie, but this mystifies me. I wondered if was the CMOS battery; I pulled the battery and reset it, which allowed the computer to restart in safe mode, but at reboot it went back to a blank screen. Hardware isn't my specialty, but the fact I can't even access the bios says I need some advice. Help?