A custom portable app is leaving data behind

There is a lot more to making an app portable than just copying it into the template and building it.

First, you need to have a decent understanding of what the launcher.ini is, does and can do. The best place for that is the PortableApps.com Launcher documentation.

Then, you need to understand how the app stores it's settings. Are they in a file (or potentially multiple files), are they in the registry, etc. For the registry part, do a search here for RegShot Portable, it is only a beta but it runs fine. You are best off running RegShot on a machine (or virtual machine) which has not previously had the app anywhere near it. Take a shot of your registry, install the app, take a second shot and compare them. This will tell you what (if any) registry entries are created/modified by the app. Some you don't need to worry about, but that is documented elsewhere in the launcher manual.

This should get you a good way to having a portable app, but if anything else comes up, check the manual, or do a search, you will more than likely find it. Failing that, don't hesitate to ask, there are more than enough people here willing to point you in the (hopefully) right direction.