Remove Windows 7OEM Certificate and Key and re-import to activate OEM certificate method

Start Menu - Search “CMD”, right click "Run as administrator" &

type "slmgr.vbs -upk" to uninstall the certificate.
Type "slmgr.vbs -rearm" to reset the computer's license status.
Then re-import the relevant OEM certificate and Key.
The basic usage of the slmgr command: slmgr.vbs -upkpb61 (help and comment)

Run cmd
as a administrator to import the key command (using Lenovo's Ultimate as an example):
slmgr.vbs -ipk 6K2KY-BFH24-PJW6W-9GK29-TMPWP
Command import command:
slmgr.vbs -ilc certificate path
other commands and their functions:
slmgr.vbs -dlv (show detailed license information)
slmgr.vbs -dli (display license information)
slmgr.vbs -xpr (default date of current license status)
slmgr.vbs -ilc lenovo.oemcert .100036.xrm-ms
slmgr.vbs -ipk 6K2KY-BFH24-PJW6W-9GK29-TMPWP
slmgr.vbs -xpr