Have you 'shared' the hard drives?
On desktop, double left click on My Computer. Select and right click on the hard drive. Select the 'Sharing and Security' option, the 'Sharing' tab and follow the instructions. You want network users to be able to move and change folders, etc, I presume? Anyway, I think the options are self-explanatory. On each computer, make the hard drives 'shared'.
If you have any further queries, please indicate your OS...