Software Informer is installed like any other application as there is no hidden way to install it. If you don't like what it does, go to Programs and Features, locate it in the list and then initiate the uninstall procedure.
I do however have it installed and am using it because it keeps my apps updated without even touching it. For example, I don't have to go to VLC Media PLayer's page to download the install package, replace the current installation, and eventually encounter other issues. The S.I. Client does it in the background while I can keep focus on various things.