Not too familiar with registry, but that's where you should be looking if you were to get rid of this installation trace.
I would strongly advise against altering the registry if you do not know what you are doing.
Download a copy of regcleaner.exe it is free, easier to use and safer than messing with regedit.
Don't be surprised if deleting any lingering registry traces doesn't work. The best you can do is delete the original install files, all temp files and clean the registry. That is only working in about 20% of the cases for me anymore.
All the shareware has to do is drop an entry a some meaningless point in the registry that says xyz with an encoded install date and you won't be able to associate it with the program.
The shareware guys are getting very good AT HIDING their markers on your system. Your best bet for new installs is to run a program in background that tracks all new files stored on your system so you can see where everything is hidden. Also one that tracks every registry change. This is a major pain so I don't bother. I think Norton can do all this but I hate Norton.