If you are using the NTFS file system it's very easy. Just explicitly "Deny" access to those that you do not want to have access (make sure not to include yourself/admin though). Not only will that work from the network, but it will also work if someone logs on locally as well. One more thing, if that directory is something that has programs installed to it, you might want to add the "System" account as have full Read/Write/Change/Delete permissions as well incase it needs access.
EP, glad to see you come back and tidy up...did want to ask a one day favor, I want to enhance my resume , was hoping you could make me administrator for a day, if so, take me right off since I won't be here to do anything, and don't know the slightest about the board, but it would be nice putting "served administrator osnn", if can do, THANKS