Okay, I held down the CMOS button for five seconds, following the directions on another page on this site. When I booted up again, I got this message:
162-System Options Not Set. Your system configuration has changed since your last boot. Addition of a hard drive, etc., or loss of power to the Real Time Clock has occurred. Pressing F1 will record the new configuration. If this message persists, you may need to replace the onboard battery.
So I pressed F1 to boot, and then I got this message:
An operating system wasn't found. Try disconnecting any drives that don't contain an operating system. Press any key to restart.
And that's as far as it goes now. Any idea what I should do?