I recently installed Office 2008 and I'm extremely displeased by the slow
operating speed of the applications.
Is there a way to reinstall Office 2004 without losing my email and user data?
Your mail is in your Microsoft User Data folder and not in the application
folder. You would need to export as Entourage archive under File --> Export
to move your data back to Entourage 2004.
You can just leave Office 2008 installed and wait for the SR-1 update. Just
be aware that you should install 2004 first. Entourage 2008 moves fonts to a
different location disabling the older 2004 fonts. If you install 2004 AFTER
2004 it will just reinstall them. When you go back to Office 2008, you will
need to rectify this problem.