I had an issue with Outlook 2003 that after installing Visual Studio Team Suite RTM & Team Foundation Client almost everytime I tried to start outlook it would attempt to run visual studio setup. It would prompt for a disk, run for awhile and then let me use Outlook. I thought I was alone until Walt Ritscher mentioned having similar problems.
I tried everything just short of paving my laptop to get rid of this including uninstall reinstall of Office 2003, Visual Studio 2005, etc.
Finally I found a forum post that mentioned re-registering a Windows Installer dll.
In short: regsvr32 "C:\Program Files\Common Files\Microsoft Shared\MSI Tools\mergemod.dll"
More information is in this MSKB article: http://support.microsoft.com/kb/329214/EN-US/