Not being cheeky, you are having problems plain and simple. There is no removal tool that I am aware of, but there is a way that might work.
Download Windows Installer Cleanup
and then install it. Once its installed, run it. Scroll thru the list (the list is in two sections depending on how the program was installed) and see if Secunia is in the list. If it is, select it and then click the remove buttn.
If that does not work, I can contact Secunia for you and see if I can get the file and registry entries so we can get rid of them.
Have you tried installing the new Secunia PSI? It might run a removal tool before installing the new version. Personally I have not used software informer, but I have used both versions of Secunia PSI. I like the first one long after the second came out, but I have slowly gone over to the dark side. I like the new version now, as long as you have an always on connection.