What exactly is path for this key? Maybe this is any null key -if yes
the best way is completely remove it,because null keys are unwanted in
the system,there is special tool regdelnull which do that 'RegDelNull'
(http://technet.microsoft.com/en-us/sysinternals/bb897448.aspx)
Another reason would be this key is used by any process -you can try
edit in safe mode.Finally solution if really nothing help is edit system
registry from WinRE -look here from post
17:http://www.vistax64.com/general-discussion/191151-cant-delete-registry-key-2.html
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Flavius
Microsoft Windows Vista