Regshot is a small,free and open-source(GPL) registry compare utility that allows you to quickly take a snapshot of your registry and then compare it with a second one - done after doing system changes or installing a new software product. The changes report can be produced in text or HTML format and contains a list of all modifications that have taken place between snapshot1 and snapshot2. In addition, you can also specify folders (with sub filders) to be scanned for changes as well. Read more.