MadClown

It's easy to reproduce using your steps, so hopefully the developers will look into this.

CCleaner has had this problem ever since Firefox started using sqlite files for storing the history, which I believe was with version 3.0. There's been a lot of updates to CCleaner since Firefox 3.0 came out and this bug still hasn't been fixed, so I don't really expect it to ever be.

If you have your location bar to show only history and then run CCleaner to clean the Firefox history, it messes up the places.sqlite file and the Firefox location bar will always display your bookmarks also even if you clear your history using the built in Firefox history cleaner. The only way I know how to fix it is either to delete all the bookmarks and then run Firefox built in history cleaner or delete the places.sqlite file. I'm using the latest CCleaner and it still does this.

The portable version of Speccy adds some entries to "HKEY_CURRENT_USER\Software\Piriform\Speccy"

I know, this is a very annoying issue that has been around since Firefox 3.5 came out and like you said its because of the places.sqlite. I've mentioned this problem before here and no one seems to acknowledge it. I wonder if the developers of CCleaner are even aware of the problem because with every release of CCleaner there has never been a fix for it, though sometimes I wonder if it's even possible for them to fix without just deleting the places.sqlite file.

I think its because CCleaner will corrupt the places.sqlite file which stores the history. The only way not to have this happen is to first clear Firefox with its own internal history cleaner, then run CCleaner after you close Firefox. But if your places.sqlite file is already messed up you have to delete it first. Doing it this way kind of makes CCleaner useless though for cleaning Firefox but its the only way I know how to prevent CCleaner from messing up the places.sqlite file. I don't know if it's possible for CCleaner to ever clean Firefox correctly, but it's been this way since Firefox 3.5 came out.

When I use CCleaner to clear Firefox browing history and cache, Firefox will always search my bookmarks from then on in the location bar even though I have it set to search my history only. To fix this I have to delete all my bookmarks and import them again. If I clear my history and cache with Firefox first, then use CCleaner, the problem doesn't happen.