While virtual machines are a possibility, they are also a bit of overkill.
Clarion has the ability to have multiple "versions" of your environment. So it's trivial to install both NetTalk 8 and NetTalk 9 into different folders, then you can open any app, and just switch between them. Test with NT9, oops there's a problem, simply select a menu item, and it's back to NT8 and you keep going. This is all done from inside one IDE.
Here at CapeSoft we make a separate environment for each commercial product, and everyone can point their Clarion at that "version" of the environment when working on that app. So it doesn't matter what you do to the clarion on your own machine, you know that when working on an app you get the environment that belongs to that app.
In addition to that I have an number of "versions" set up locally - 18 of them on my C-drive alone.
This is soooo easy to do that frankly no doing it is just the height of laziness.
a) copy your clarion folder into a new folder (I've got c:\clarion10, and c:\clarion10NT8)
b) In the IDE menu, Tools, Options, Clarion, Versions
c) In the drop list at the very top of the window select "<new version>"
d) select c:\clarion10nt8\bin\clarion.exe (wherever your new version is.) I also give it a descriptove name to easily identify the version later on.
that's all.
Now you can change between versions by just going to the Build menu, Set Clarion Version, and change between them.
If you get a 3rd party upgrade you can choose which version to install it into, so it's easy to keep one version at NT8 for safety and another for NT9.
Hint: This also works _across_ clarion versions. So you can have a Clarion 9.1 version inside the C10 IDE and so on. Makes upgrading from one version to the next super simple.
Cheers
Bruce