If these users are accessing these files through a share then do the following.
1. Let them know you are about to kick them off.
2. Change the permissions for the share (not the files) by adding Everyone No Access (this way you don't have to change any of the existing share permissions.
3. Use Server Manager (or Control Panel/Server on the local server) and kick everyone off the server who didn't take heed of your warning. The No Access permissions on the share will keep them from reattaching.
4 Do your update. Then take the No Access off the share.
If there is an application causing the locked files then you will need to disable the app during the update.
Hope this helps...