Virus??? I am not sure

Hi

I have Windows 98 on my PC. Lately, Windows Help gets fired up on its own, Other running apps have their options toggled. Suspecting a virus, I got an antivirus and scanned the system. Sure enough, it detected two viruses. So, I downloaded a dos-based antivirus to a clean system along with a boot floppy from the sam system. when I booted from this floppy, after some time, junk characters started appearing in the command prompt. I tried booting into Windows, but the display has changed from 24 bit color to 16 colors!

Is this a virus? Or is something wrong with my hardware??

The antivirus is executed from a CD.

Regards
Sridhar