I've recently built a new development environment for a new InfoPath 2007 and Windows Workflow project. The installation of all the software was going really smoothly until I tried to install Visual Studio Extensions for Windows Workflow Foundation. Each time I would double click the exe to install the extensions I would get the repair and remove application for VSTO 2005 SE. I couldn't figure out what was causing the strange interaction so I deleted the install file and downloaded it again but no luck because the same thing was happening with the new file. I rebooted the server but I still had the problem and I finally decided to move on and install the reset of the software. When I was done I deleted the all the files except for the VS 2005 Extensions for WF and I tried it again and it worked this time. Instead of installing the extensions I decided to do some more investigation on what was going on and after doing some trial and error I was able to replicate the strange interaction. The strange interaction only occurs when the VS 2005 Extensions for WF and VSTO 2005 SE installation files are in the same directory. If you remove the installation file for VSTO 2005 SE from the directory the strange interaction doesn't occur and you are able to install the extensions successfully.
I don't know if anyone else had or will have this strange interaction but I thought I would pass along my experience.
mlotter