Thanks, KJxp! Just made myself a couple of little .reg files, and they work a treat! sec-tab-on.reg adds the value that turns on the security tab: ---cut--- Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot\Option] "OptionValue"=dword:00000001 ---cut--- sec-tab-off.reg restores things to the way they were before sec-tab-on.reg was merged: ---cut--- Windows Registry Editor Version 5.00 [-HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot\Option] ---cut--- My machine (unusually for an XP Home box) is set up with a single Admin user and a handful of limited accounts for me and the rest of the family to use day-to-day. The limited accounts can't make changes under HKLM\SYSTEM\CurrentControlSet\Control\SafeBoot\, so the above .reg files only work from Admin (which is exactly what should happen). Interestingly, if I merge sec-tab-on.reg and then switch out to the Welcome screen, the only users that appear on it are Admin and Administrator - exactly as if I'd booted into Safe mode. It seems that rshx32.dll isn't the only thing that looks for this value.