My SpyHunter program says this about PurityScan. I know it's poor grammer....
PurityScan is a program that scans your computer for objectionable Adult Content, then permits you to eliminate it. Sadly, its an excellent idea, but it installs Adware instead. You are allowed opt out of their e-mail list, but they don't know is to tell you is that the install file copies itself, and goes on startup. You will get a pop-up every 3 minutes or less. The true file was called sear1.exe, but they have changed it to setup.exe. This is usual file name, and if found, check that file before eliminating it.
http://www.softsecurity.com