|Install Watch PRO|
This tool takes a snapshot of your computer and will then analyse differences after.
It will help identify changes made by any installation process.
This tool is free and generally works very well, you can download it from "http://www.epsilonsquared.com/installwatch.htm".
Other similar tools are listed at my "setup capture tools links" page.
The "SysInternals" site is one of my favourite sites and has many free tools (such as "FileMon.exe" and "RegMon.exe") which can help identify install activity and diagnose issues such as missing files and registry.
Monitoring without any tools other than a comparison tool ("WinMerge.EXE" or perhaps your eyes!) is possible. Registry can be exported in text format (its sorted) with many tools including "REGEDIT.EXE" and a sorted file listing can be created with "dir c:\ /s /on /a >somefile.txt". My "IisDumpMetaBase.VBS" can produce a text file representing all or part of an IIS metabase. Do not ignore the possibilites of text comparison! In some situations this is actually the easiest approach!