Re: Local Users/Groups manager. I just noticed you have Home Premium. The manager is available in 7 Professional, Ultimate, and Enterprise editions. Sorry.
for additional info.) To confirm that it's not available, click Start > right click Computer > Manage.
If SFC found an error it's recommended to run the scan 3-4 more times. If the error is still unable to be fixed it wouldn't hurt to post the CBS.log file.