Microsoft Office did not install correctly.

That sentence was the bane of my existence for the better part of my Saturday morning; but after a little bit of reading on Google and some general know-how, I made it work.  If you’re running into this problem, do the following steps:

1. Uninstall Office: Go to Applications/Microsoft Office 2008/Additional Tools/Remove Office and run the uninstaller.
2. Delete the preferences file: Go to Users/username/Library/Preferences/Microsoft/Office 2008 folder and delete the Microsoft Office 2008 settings.plist file.  Note: This was a step that I found on Google; while it’s apparently been successful for others, I had to delete the Office 2008 folder that contained the .plist file before I was able to get it to work. The installer will re-create this folder, so don’t be afraid to try this step!
3. Empty the Trash: The OS may still try to access files from the Trash, especially when the installer is searching for previous versions.  This is just a precaution.
4. Reinstall Office: Run the installer from the CD.  You’ll know it worked if it asks you for your CD key during the installation steps.

During my research, I found that people have experienced a variety of results with this procedure.  Some have been able to install without uninstalling the trial, and some had more problems than I did.  As with any troubleshooting, your results may vary, and you may have to make some things up as you go.  Good luck!