Portable RegShot is the portable version of RegShot, registry comparison made easy. it can run from a USB flash drive or any other portable device.
This app is a small 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.
As a plus, you can also specify to scan folders and subfolders for changes.

The license of this software is Freeware, you can free download and free use this registry cleaner software.