how to disable print screen in windows xp or 7

have a look here
 
http://labnol.blogspot.com/2004/08/disable-print-screen-key-in-windows.html
http://forums.techarena.in/windows-security/744033.htm 

According to the comment of DarkXiphoid and LeeTutor, there are two ways to do what your want.

DarkXiphoid's comment:-

"you could disable the buttons

Printscreen:
http://labnol.blogspot.com/2004/08/disable-print-screen-key-in-windows.html

Just remap both keys (and all the other keys you like) to whatever you think is funny ;-)"

LeeTutor's comment:

"There is a free program you can download called AutoHotkey that you can use to automate many tasks in many different ways.  One of the things it does very easily is remap keys on the keyboard.  You download the program here:

http://www.autohotkey.com/

After you install the program, you can read the documentation built into it to learn how to "program" the remapping of keys.  The scripts you create can be "compiled" into .exe files which can then be run at system startup by creating a shortcut in the Startup folder on the Start Menu.

This is a quotation from the builtin help file about remapping keys:

The syntax for the built-in remapping feature is OriginKey::DestinationKey. For example, a script consisting only of the following line would make the "a" key behave like the "b" key:

a::b

The above example does not alter the "b" key itself. The "b" key would continue to send the "b" keystroke

To disable a key rather than remapping it, make it a hotkey that simply returns. For example, F1::return would disable the F1 key."

Source: https://www.experts-exchange.com/questions/21943437/Ctrl-and-print-screen-command-on-Windows-XP.html?sfQueryTermInfo=1+disabl+kei+print+screen+xp

........To disable these functions all you have to do is register the hotkeys, which causes Windows to send your app a WM_HOTKEY message when the user presses either hotkey. Your implementation can ignore the message to bypass the default screen-capture behavior. A good place to do it is in your mainframe class.
.........
the question is how??

dan it is not working should I restart the pc?

Yes.

After you edit the registry, it needs to restart XP to take effect.

10x