The VSE installer, setupvse.exe, makes use of our own competitive uninstaller code. We call it "UNI".
It runs on any platform that supports VSE, but requires that you use setupvse.exe to launch the installation.
If you are not using setupvse.exe, then you will need to take your own measures to ensure no competitor or other incompatible products are on the system - which could also include older versions of our software. Else you could end up with 2 products installed.
If you are using setupvse.exe and you have a product that is not removing, it may be a product we do not know about yet - the intelligence of UNI is only as smart as we make it. We endeavor to keep it updated each time we repost the product to the web. The repost package that will include Patch 3 will also have an updated UNI; and actually will include some improved intelligence for detecting certain competitor products so we don't have to update it all the time :).