How the protection would be with the two anti virus software for the single system ?

level of protection from viruses

How the protection would be with the two anti virus software for the single system ?software

Using two AntiVirus programs is fine as long as ONLY ONE of them has any active scanning enabled. Do NOT set up more than one AntiVirus to run in the background. If you are unsure how to configure your anti-virus software, you're better off just using one. More than one can grind your system to a halt if they are both active. They will conflict with each other and cause many problems. It's best to just get one reliable AV such as BitDefender or Kapersky. Norton and McAfee, while the most well-known, are by NO means the best AV programs. Free AV programs such as AVG and Avast! are much better.

*IRT ELfa Geek

["If you try to run two Anti-virus programs at the same time on one PC, each sees the other as a Virus and all they do is try to stop the other one from working."]

This is not true. As I said above - it is perfectly fine to have more than one AntiVirus utility installed on your computer - it is NOT okay to have them both actively scanning for viruses in the background. Only ONE of them should have any active scanning features enabled. You can run scans with both, just not at the same time. Though, if you were to use a really good AV, the need for more than one is eliminated anyway.