You have seen varous ways to lock / unlock users from SAP R/3 4.6x. It can be directly performed by mass change options. Please find the procedure below.
Tools --> Administration --> User Maintenance --> user (i.e. SU01) Step 1: Select Menu Environment --> Mass Changes. Step 2: Click "Address Data" button Step 3: F8 (execute) to select users to be locked. Step 4: Select users to be locked and click "Transfer" Button. Step 5: Click Lock / Unlock icon to lock or unlock the selected users.