I can think of 3 ways to achieve my goal:
Create a clean VPC, install a given piece of software, and compare the before and after states.
Somehow reverse-engineer the installer.
Somehow redirect the output of the installer in question so that all registry calls and copy/move file commands are recorded, but not executed.
The first option can be done manually, or potentially automated, but I feel it's rather OTT for my needs. The second could cause all sorts of licencing issues, not to mention it may not always return a correct result. Also, without delving into hex editing, I can't think of a way that it would be possible to do manually (some installers - eg Anti-Virus software - may react unfavourably on automated attempts to investigate the installer).
The third option shows the most promise, although if the first could be stripped down into a lightweight throwaway environment, it would work pretty much the same way. However, I'm not sure how to do it. So my question is:
What tools are available (if any) and/or how could I find out this information manually?
I'm not looking to reverse-engineer anything (if I can help it), but I just want to know exactly what changes are being made to my PC by a given piece of software.