You have to take ownership of the Legacy key in order to remove it.

Right click on the key and select Permissions.  Click ADD and add your user name and click OK.  Click ADVANCED and select the tab for OWNER; select your user name you just added and click APPLY.  Select your user name on the main permission window and (in the bottom window) click on FULL CONTROL in the Allow column.  Click APPLY on the main window (and OK if it does not close automatically).  Do the same for any sub-branches (keys) under the main key.

Right click and select delete to remove the key(s).