Hmmm....assuming you are running windows, there are a couple of ways:
1. Hit Start---->Run and then type cmd or command if you are using anything pre 2k. When thd dos box pops up type (without the hyphens) "net use /?" for a list of command line net use options. I beleive you would want to put in the "/delete" switch.
2. You could just right-click on network neighborhood and select "Disconnect Network Drive" Then pick the one you want gone...
Hope this helps some
/JD