Changing CMOS settings can be useful -- or dangerous. Resetting the time and date isn't hard; but if you select the wrong wait-state setting, for example, you may lock up your PC -- a problem that can take many hours to fix. So use caution when working with the CMOS Setup program.

First, back up your CMOS settings -- and not just as a safeguard against making unintended changes. When your PC is off, a battery on the motherboard constantly refreshes the CMOS settings. But when the battery dies -- and they all do, eventually -- so do the settings.

Some CMOS Setup programs come with a backup feature that writes your settings to a floppy. If yours does, use it. If not, try software that backs up CMOS settings; candidates include Norton Utilities and a number of shareware programs. CMOS settings aren't standardised, so many of these programs -- including Norton Utilities -- only capture certain core settings common to all PCs.

Next, make a hard copy of your CMOS settings. If your PC is connected to a printer, try pressing the <Print Screen> key to get a hard copy of each screenful of information in the CMOS Setup program. If that doesn't work, sharpen your pencil and start writing it all down.