text: how is it i have to have several different spyware programs to get rid of the stuff that gets put on my comput i had norton everything, adaware, and the yahoo toolbar.  these have served me for awhile.  then somehow a bunch of adware and a trojan got by all of this and my firewall and infected my computer badly.  i had to uninstall  norton and install defenderpro.  why did that happen, when i paid good money to be protected? i agree with norm on norton. this site will answer your question, great information , i put a very small part of some of the information below, check this site out to get a better understanding to the question you asked..  http://www.techsupportalert.com/free-vs-paid-av-part2.htm (it's a fair question. the current security threat is so great that you can argue that pc users should be protecting their machines with the very best products available regardless of whether those products are free or commercial.  in this multi-part series we'll look at the best free anti-virus scanners, anti-trojan products, spyware detectors and see how they stack up.   1. no computer security product is perfect; all products have less than 100% detection. the choice between products commercial and free products is thus not a choice between perfection and something less rather it is a choice between differing levels of imperfection.  2. in absolute terms the best commercial av products such as nod32 do have higher detection rates than the best freeware versions. however the difference between the rates is relatively small.  3. by combining two or more freeware products it is possible to get better detection rates than the best commercial av programs used alone.  4. layering is an attractive option for improving malware detection rates and may well offer greater opportunities than concentrating on looking for a near-perfect single product.  in the next part of this series i'll look at the effect of adding even more layers of protection)