Running Office 2003 and 2007 at the same time

Good morning, Experts.

I know Office 2003 and 2007 can coexist on the same system.  But I am having a horrible time making certain programs work after getting them both installed.  Primarily Outlook.  After doing a bunch of random things, I manage to get both working.  But I suspect there is something that I' not doing right or should be doing to make both work in the first place.

My user environment is such that they have to access an Access 2003 DB while pushing documents into Word 2003, but getting their mail in Outlook 2007 and having the ability to take those Word 2003 docs and send them directly to email.

Does anyone have any suggestions or wisdom on the matter?  Help is greatly appreciated.

Thanks.