When working remotely from a Windows client, pressing ALT-TAB by default doesn't switch you to a different remote window, but minimizes your NX session window.

Starting from NX Client version 3.0.0, you can disable the catching of Alt-Tab and PrintScreen keys by configuring your session:

• Run the NX Client Gui.
   
• Select the Grab the keyboard when the client has focus checkbox
  in the NX Client GUI -> Advanced tab.
   

If you are running NX Client 2.1.0-17 for Windows, you can use the
Ctrl + Alt + K  key combination to enable/disable the catching of Alt+Tab and Print Screen keys within the NX session.

If you are using NX Client  2.0 or 1.5, you might be interested in a small utility
that has been written to allow NX Client to pass ALT-TAB combination(s) to the remote window manager, instead of being captured by Windows. The program ("NX ALT-TAB" or 'nxat') hooks the appropriate keyboard and forwards the ALT-TAB combinations to NX Client.

The binary and source can be found at:

http://majuric.org/software/nxat/

and a short readme at:

http://majuric.org/software/nxat/readme.txt

Important: recent user findings have shown that there is a bug in this utility that stops it from working with client 1.5.0. While we are making a patch available, users can also refer to the following link which provides the utility without the bug.

http://ssrini.netfirms.com/