I have until recently been running a Internet security software but my OS seemed to be running slower so I removed it and put on Avast 4 free anti virus and a anti spyware called Spyware Detector, both found unwanted viruses and spyware which the Internet security software did not catch and delete, I think it was 60 items for the anti-spyware and 2 items for the anti Virus. My question is how do you know with what efficiency will different software protect my PC as all the manufacturers tell you theirs is the best.

At the moment the OS is just zipping along , but would like some professional advice on the matter.

There are many independent companies and individuals that perform impartial testing on security software using both known threats that should be in the antivirus signature files and news threats that the software heuristics engine must help to detect. One site that performs such tests is AV Comparatives.

A similar site exists here for antispyware.

PC Magazine about Spyware Detector:
http://www.pcmag.com/article2/0,1759,2073458,00.asp

Max Secure Spyware Detector 2.0 is speedy and reasonably good at cleaning up infected systems, but poor at keeping spyware out of clean systems.
Limited ability to block the installation of spyware on a clean system. Display of found threats is awkward. Confusing terminology.