When you try to use Explorer.exe after applying SP5, you may receive:

This operation has been cancelled due to restrictions in effect on this computer. Please contact your system administrator.

Shell32.dll was improperly updated. It no longer works when NoDrives is set to hide the system drive.

To work around this problem, use either:

1. Use Shell32.dll from SP4 until SP6 is released. See tip 0181.

2. Remove the restriction from the system drive.