Win95/98 quirks?

On two systems, one running Windows 95 OSR2.5 and the other Windows98SE, at random intervals, the computers will attempt to access the floppy drive, causing the most annoying racket. I thought it might be the anti-virus program but the second call on the Windows 98 system leads me to believe that the answer may lie elsewhere.
Any idea?

Other problem. On windows 98SE system, all of a sudden the mouse does not pick up the selection from pull-down menus but the contents of the screen under themenu – as though the menu was not there. This quirk seems to occur in Outlook Express and Excel 2000, at least that is where it has been noticed.
Any idea?

Thanks for your help.

gilles mailhiot