RegShot is a small, free, open-source 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 folders) to be scanned for changes as well.