Try the registry merge here:
http://www.sevenforums.com/tutorials/197908-power-plan-specify-default-all-users.html
The one under the caption “To Allow Users to be able to Specify Their Own Power Plan”. Tried lots and lots of things, this worked. Its contents are below. After the merge you may have to log off and on or even reboot, before the fix will be operational.
Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Power\PowerSettings] "ActivePowerScheme"=-