IE7 Blocker Toolkit
 

http://download.microsoft.com/download/0/1/3/013113f4-700b-4854-a6b7-54083563c146/IE7BlockerToolkit.EXE

You can either setup a batch file to run in your login script to disable it in the registry:

IE70Blocker.cmd localhost /B

or (my personal favorites)

Import the Group Policy template (ie70blocker.adm), and disable it from there.

NOTE: The IE7 install will be blocked until the registry key is removed or toggled to enable install.

IE70Blocker.cmd localhost /U