Ok.. I'll try to help:
You don't say what OS you are using, so, assuming something recent like XP or 2K:
Open up Windows Explorer. Chances are it's going to take you straight to the A:\ drive... If it does, just click on the C:\ drive, wait till it displays the folders there, and then close Explorer. Hopefully, that will work. If not, try holding either the CTRL or SHIFT key the next time you close it after doing the same thing I suggested above.
If you are using Windows 98, you can go into the Control Panel, and go to the System Settings, (or right click on my computer and select properties) and then go to the advanced tab. Somewhere in there, is a setting to check for the Floppy Drive. Uncheck it. Windows 98 gurus: It's been a while since I used that OS, so if you can be more specific, please help out! :)
Hope this helps!