Identify system changes between dates

[trids]

A few weeks ago I came across a free app that included as one of its features the ability to help identify changes to the system .. but now that i need it, i can't remember what it was

I seem to recall it might have been a PPC registry editor that runs on the desktop, but I might be confusing it with something else.

Any ideas? Any app that can identify what changes occur on the PPC would help.