I locked out myself by adding something in "Run only specified windows application" in gpedit.msc. I am running windows 7 Enterprise 64bit. I am logged in as administrator but can't run anything including cmd.exe, mmc.exe, gpedit.msc, or regedit.exe.
I can't manage my user accounts.
I'm pretty sure that's (only) a User-level setting (HKey Current User). If you edit it for just your user (via local polices) then you may be able to simply log in as a different administrator account and undo it for the related user hive (via the registry).
If you're doing it by editing the registry, that GP controls the HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer registry key.
If that doesn't work, then another option is to log into another computer on the network, and then use either GPEdit.msc or Regedit to remotely undo the restriction list you implemented.
To run GPEdit.msc against a remote computer, you have to run it form the command-line as such:
gpedit.msc /gpcomputer: Computername
