Exactly what Emerald said. One antivirus will see even the small snippets of code (called signatures) that the other uses to identify viruses as viruses and as such it will prevent the installation. Personally I'd also switch from AVG to Avast. Reason for that is that Avast is and always has been free whereas AVG is constantly nagging to upgrade to the paid software. I am the network support tech at my workplace and we run AVG as that's what my boss wanted us to run for some god forsaken reason. Having to disable that notifcation was a huge PITA requiring registery edits and other such things to prevent that specific code from loading.