Phil, it's often needed to do some SW experiment, so I put my main HDD in a removable case and when i need to do some IMPORTANT upgrade or installation, I quickly substitute my main HDD with another 'sparring' HDD with the same content.
In this manner I can do any kind of operation riskless.

Anyway I always have an (fresh) image copy (on external HDD) of all my HDD partitions.

I also use True Image 11 that has an useful function called "try and decide": it use a ghost partition and any operation is addressed to this 'ghost' system (like Sandbox). When you reboot, all the changes are gone!

Gianrico