My question is about AVG Antivirus 7.5 FREE Can it ...

I know someone who has AVG and Norton Internet Security on his computer, and they both work fine, with no problems.

 No antivirus program is 100% effective, and most programs catch viruses that the others don't. So it makes sense to add another layer of protection.

I am not familiar with Blueyonder PC Guard so I can't really tell you if it can run  with other antivirus software without causing any conflicts. I know that many people recommend combinations like NOD32 and AVG, so it is worth giving it a try.

You'd better not combine two different antiviruses instead you want critical slow down and look for problem

 But you're right an effective way to achieve good protection is to scan your files with different program

 Some antiviruses progs use two different "motor" to inspect files but it's managed internally by the program itself not by the user

 There are other tricks to use (scanning your file remotely or using a Livecd) but you need to have some good computer knowledge to achieve this

Never use two different ant-virus protections.Even with two Firewalls installed you can get a lot of trouble.My wife could not open her E mail. The thing to watch is doing daily updates and at least a full scan every week.Paul