So far from my experience i noticed that when it comes to installing and uninstalling casino software RTG is by far the most quality one. One of the rare things it has is Digital Signature and i never had any problems unistalling it from a Control Panel.
The main problem IMO is tied to the fact that casino software in general is very poorly optimized for newer versions of Windows (like Vista and Windows 7), especially if you have a lot of casinos installed. They tend to root inside of system 32 folder and they stay there even after unistalling. If you are not a computer expert or simply dont have time for additional maintenance effort, i recommend reinstalling your system from scratch. It might be radical but in the end its the easiest solution.
Also if you are Win Vista or Win 7 user, i strongly advise against registry cleaners, there is still no good one on the market that will not mess up your system in the process.