there is some more info about this on the Windows Vista forum here clicking run as admin doesnt always solve the problem - I now use a small download called take ownership but sometimes I still get access denied
Try Start > type "Control Userpasswords2" in the run/search box > Press [Enter].
Double click your username, and go to the "Group membership" tab, and select Other and change the combo box to Administrators. Select OK, and OK. . . :-)
U can also try to type "Services.msc" in the run box and Pres Enter, then scroll down to "System Restore service" and double click it. Go to "log on" tab and select "Local system acount" and OK, try that then if still not work then go back to that "Log on" tab in "Services.msc" and instead of "local System Account" try "Other2 and type for the username: "Administrator" (With out the Speechmarks) and make both the password fields blank.