Did you reboot after disabling UAC?
Open a command prompt with "Run as Administrator". Run this command sequence. Do you get an error?
cd \
md Test
dir /ad T*
Even though your account is a member of the Administrators group, the explorer process does not run elevated. This looks like a UAC problem.
I would recommend that you keep UAC enabled. Re-enable it, reboot, and then try that command sequence again.