Printers that use ports that do not begin with COM, LPT or USB are not redirected in a remote desktop or terminal services session. To force all ports to be redirected, the filtering type has to be changed. This is done in the registry.

1. Do a Start, Run, type in regedit and press Enter. This starts the Registry Editor.
2. Navigate to the key: HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\Default\AddIns\RDPDR.
3. Right-click in the right pane, choose New, then DWORD value.
4. Name the value FilterQueueType, press Enter.
5. Double-click the newly created entry, and set the value to FFFFFFFF, click OK.

Restart the client, log in to your session, and all ports should be redirected.

Filter values

You can use other values to set the FilterQueueType to filter in/out other ports:

• 1 - all ports that begin with LPT
• 2 – all ports that begin with COM
• 3 – all ports that begin with LPT or COM
• 4 – all ports that begin with USB
• 5 – all ports that begin with LPT or USB
• 6 – all ports that begin with COM or USB
• 7 – all ports that begin with LPT, COM, or USB
• FFFFFFFF – all ports

Starting from RDP 6.0, this setting is no longer valid.

Source: http://support.microsoft.com/kb/302361.