It says in some donate option that the guy thinks protection on the computer should be free to everyone, but to make advances and have a job donations are gratefully accepted.
On a machine infested with malware, multiple programs are preferred. Ad-AwareSE and SpyBot have been mainstay's for years and do vary well, but NO single program will get it all! They are both free as well as the Microsoft product (also very good), with the exception that the MS product uses a real-time scanner, whereas the other two don't, (free versions). I run both of them as a first response to cleaning malware (see the sticky ).