As your other reader mentioned, AVG is a good choice, although I did have some problems with viruses getting through it. I changed to AVAST 2011, also free, and have had no problems since. Also, no software does seem to be able to stop all, so I also use Malwarebytes free edition, and between these two softwares, haven't had a problem in 2 years. There is a site called download.com which has a wealth of both pay and free software of all kinds, and a user-friendly search engine. All the software is shown with features, both editor and users reviews, and is available for download. The only thing to watch out for is whether it is listed as free or pay. If it is pay, then typically it downloads a trial version. You can find what you need there.