Installing Outlook Add-ins

Hi,
I'm trying to install an Outlook Add-in (GTD, from David Allen and Netcentrics), but when I try to install it, the Add-in installer tells me that there needs to be an installation of Outlook 2003 or later installed in order for me to use the add-in. In other words, the add-in doesn't see my installation of Outlook 2010. Originally, the installer downloaded to a folder inside my Mac's file system. I've tried running it from the desktop as well as the 'C:' drive, and it doesn't see the installation of Outlook when I launch it from there either. Can someone tell me what I'm doing wrong?

Thanks in advance for any help!