I , along with a number of other people had a fun time getting this to work.
We were presented with:
Not very helpfull!
In my case I had to shut down One Note quick note in the system tray, MSN Messenger and Search and finally the Office 2007 Download application.
The funcontinued when downloading the Desktop Search for Outlook as that needed 4 stray processes to be shut AND Explorer.exe!
It all worked in the end but wow does the whole install routine need some major work. At least the product seems rock solid so far and worth every bit of pain!