This is a bug (feature?) of windows 98 and 95.
It is caused by having one or more drives hidden in my computer.
You need to go to Tweak UI's my computer tab and be sure that the check boxes for ALL drives are checked, even if the drive is not installed on your system.
Click OK or Apply to save any changes.
You might have to restart your computer to see any changes.

It is one of the power toys from microsoft.

Information about Tweak UI is available at
http://www.jlilest.com/tweak.html#tweak

Tweak UI is on the windows 98 CD:
D:\tools\reskit\powertoy
substitute the drive letter of your CD ROM drive for the D.

As of 3/30/1999 it was also available at
http://www.winmag.com/win98/software.htm

There is a microsoft knowledge base article on this at
http://support.microsoft.com/support/kb/articles/q188/2/09.asp