How to find out what program took over control over Print Screen key?

Solution 1:

The utility Hotkey Commander should be able to show which application has claimed Alt-PrtScn.

You might also try the following.

Why does the Print key not work in some windows?

If you are using Windows Vista or later and have Greenshot running without admininstrator privileges, while the currently active (i.e. focused) program window is running with administrator privileges, Windows’ User Account Control will not notify Greenshot that the Print key has been pressed.

However there are some easy workarounds for this problem:

• Run Greenshot with administrator privileges.
• Click somewehere else (e.g. task bar) to deactivate the current window, before hitting the Print key.
• Use Greenshot’s systray context menu to create a screen capture.

http://getgreenshot.org/faq/why-does-the-print-key-not-work-in-some-windows/