In deleting certain keys, error while deleting key appears.
Because the permissions are SYSTEM (I wonder if someone else has more permissions than me!!).
To take a simple example, right-click a key and click permissions
Click on the advance.
After clicking the Owner
My user name is yanyu, so click second yanyu(yan\yanyu) on the check mark Replace owner on subcontainers and objects and click Apply and OK
To go back to this screen, click Add…
Click on the Advanced…
Click find now and find the last yanyu (the one with only one head)
just click OK
Give the tick under yanyu (YAN\yanyu) Full Control
Click OK