The CMOS (Complementary Metal-Oxide Semiconductor) error message is referring to a battery-backed chip on your motherboard that holds hardware configuration information. This information is ALL important.
Protect this data. If you don't have a program like Norton Utilities or Nuts & Bolts that backs up the CMOS information, you need to print it out or write it down: Enter the PC setup program by pressing Delete or some other key (often noted on screen) early in the boot-up process--before Windows starts loading. Go to each screen of the program and press Print Screen to make a printout, or write down the info.
About that error: Your PC generates the error if it thinks the CMOS information has changed without your having changed it. A virus, a dying battery, or a one-time anomaly can cause this situation.
When you get this error message, you need to restore the CMOS settings. If you have Norton's or Nuts & Bolts' Rescue Disk, reboot from that emergency boot floppy and follow the prompts. If your backup is on paper, you'll have to enter your system's setup program and restore the settings manually. If you don't have a backup, research your system's configuration using printed documentation, or call the vendor.
When you've reentered the information, save your changes and boot your PC. Make sure everything is working properly, then close Windows and turn off your computer. After a few minutes, turn it on again. If the error returns, you've got a dying battery. You'll have to open your PC, find the battery, and replace it--or find a technician to do the job for you. If your battery is soldered on to the motherboard, you'll have to replace the motherboard, too.
Unless you have confidence in your soldering or want to take it to the local Computer Shop
(Computer batteries last about five years.)
If the problem isn't the battery, update your antivirus program and run a scan. Todays Motherboards come with new "Flashable" Bios technology. The downside is there is a "Block" removed that allows viruses to infect your Cmos/bios.
Other things to try if you still have the error.
Check your System Files and Delete Windows 98 uninstall information; if you find either of these. Uninstall un-necessary files.
ROOT DIRECTORY GARBAGE.
In Explorer, go to C:, select View, Details, click the Type header, and use a text editor (like WordPad) to look at files with the extension .txt, .old, .log, .prv, or .---. Chances are they're all deletable. If you regularly back up the Registry, kill System.1st. If you don't dual-boot, delete any .dos files.