source: https://www.securityfocus.com/bid/945/info

The default permissions applied to the directory containing the SMS Remote Control executable allow any user to replace the executable with any other executable. The new executable will run with System privileges after the next reboot.

Replace %SMS_LOCAL_DIR%\MS\SMS\CLICOMP\REMCTRL\WUSER32.EXE with a copy of wuser32.exe. After the next reboot, User Manager will run at startup with System privileges, allowing the logged-in user to add their account to arbitrary groups, including Administrators.