I am a user where IEs default page has been set to the parent companies nonworking intranet site, and the permissions will not allow us to change it to msn, yahoo, etc.
If the permissions have been set up to prevent changing your homepage, they have also probably been set to prevent editing the registry. If not, however, you can change this registry key to change the homepage (be careful when editing the registry, because any errors can cause serious problems):
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