I don't see the relation between FAH and Office. I have installed both back-to-back numerous times and never had any issues. I don't think AVG can be the culprit too (simply uninstall and check it out). The only software I don't know is Xfire.
Have you tried running the apps as Administrator (shortcut/advanced/run as admin)? Vista loves that.
You've already done something similar, but this could help:
KBAlertz.com: (838687) - Describes that the Everyone group of the Microsoft Office registry subkey is not set to full control when you install an Office program. Includes a suggested resolution.. This too:
Microsoft office has not been installed for the current user [Archive] - MCSE.
Have you tried turning UAC off?
John
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