Since you have a hardware firewall you dont need to use the winxp firewall. on the front desk machine open "my computer" right click on the drive(s) you want to share. click the sharing and security. click the link that you understand the risk of sharing the root of the drive, or share specific folders. on the next page check box share this on a network, then check enable users to change files.
Depending on your file system.. you may want to add the user names of the laptop into the user list on the front desk machine
That should do a one way connection, or set up an administrator account with password on the desk machine and enable remote desktop connection