I love installing beta bits. Usually I will spin up a new VM and install the stuff there, but apparently I didn’t do this with Microsoft Visual Studio LightSwitch Beta Edition. While LightSwitch is a cool idea, it’s not for me and I’m sure I uninstalled it right away. A month or so go by and the Windows Phone Developer Tools 7.1 Beta bits are out, so I go to install them on my development machine, only to be greeted by this error dialog.
“Incompatible products Setup has detected that following incompatible version of products or components are installed on your machine… "*Microsoft Visual Studio LightSwitch Beta Edition – ENU”

I checked Add/Remove programs and LightSwitch was not in the list. Hmm, I think, perhaps there are some leftover files. So I opened up Search Everything (one of my favorite tools) and did a search for “Microsoft Visual Studio LightSwitch Beta Edition”. I found tons of file folders all over the place, and deleted them all.
Running the install again, I got the same error, so this time decided to check the registry with RegEdit. Searching for the same string, I found almost 30 registry entries that had not been cleaned up by the uninstall process. I backed up my registry, then went and deleted all of those keys.
Starting the install again, gave me lots of love and I now have the Mango Dev Tools installed on my machine.
Hope this helps you out if you run into the same problem.
James