Step 1 Add a new user using current ‘Windows Login user name’, e.g. PBTECH\Michael , then Stop SQL server
Step 2 Change the server into single user mode, by add “;-m” at the end of path under SQL server property window advanced tab
Step 3: Save & restart, login to SSMS with windows authentication
Step 4: Give the new user added in step 1 System admin permission by executing :
Step 5: Under security- login find the locked user, reset password and untick the lock, save and close.
Step 5: reverse step of step2, change SQL server back to multi user mode
The SA should be unlocked.