Okay, I'll be the first to admit, I tried to install CTP3 on a machine without first cleaning up the CTP2 bits. My primary motivation was to be able to query the catalog views to detect any metadata changes that I hadn't already talked about here. As you might have guessed, this experiment did not go well.
In a couple of cases I have installed CTP3 quite cleanly on new VMs. I haven't installed Juneau yet on those, because I'm a little nervous about what exactly that will do to Management Studio… and I need at least one VM where I can rely on full functionality there. I'm getting there, but I wanted to address the case where CTP2 *was* installed.
In cases where I would prefer to keep my existing VM (which has various other ongoing work other than Denali, making it infeasible to roll back to some snapshot), I've resorted to removing every single CTP1 or CTP2 piece of software using Programs and Features (nee Add/Remove Programs). Once I had removed CTP2 completely, I ran a repair of CTP3. I then realized that I didn't have Management Studio (because the complete removal of CTP2 included shared features such as client tools). So I ran setup again, adding the Management Tools and a few other odds and ends to the instance.
Now, with all traces of CTP2 gone (including Juneau), and a now functional CTP3 and Management Studio, I thought it was time to install Juneau. No problem, I go for the web installer, located here:
Unfortunately, all signs indicate that this is going to try to install CTP2:
Fellow MVP Juan Alvarado pointed me to the registry key that was causing this problem (thanks Juan!). It is one of the things that the CTP2 of Juneau did not clean up through the normal uninstall process. The key is:
It will have a value of some folder on your machine (I changed the value to foo because my path was really long)… just change the name of the key to something else, or delete it entirely, and run the web installer again. You should see the right platform now:
I can't fault the team for this problem at all. I shouldn't expect CTPs to remove cleanly, and should know not to put CTPs on important machines or VMs that can't just be rebuilt as needed.
Ultimately, what you *REALLY SHOULD* be doing is installing CTP3 (both engine components and add-ons like Juneau) in a clean virtual machine. But I know how it is, it isn't always practical to dedicate an OS this way. So hopefully this helps some of you work around the issue.
In addition, I am in no way guaranteeing that Juneau will *work* – just that you should be able to get it installed. Once it's installed, I'm afraid you're on your own. If it doesn't work correctly, please read the previous paragraph.