If you try to take a screenshot in Windows 7 Media center by pressing the Print Screen key you will just end up with a black image.
Fortunately the fix is just a quick registry tweak away.
First close the Media Center application and then click the Start Orb, type Regedit and then press Enter and navigate to:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Media Center\ Service\Video
Then just add a DWORD called EnablePrintScreen and change its value to 1.
Close Regedit and then restart the Media Center application.
I tested this on Windows 7 x64 Media Center.
Source: Tech Hail