Sorry to but in....but I've got an idea (and I work in IT, so nerr).
1. Download the new new version of AVG.
2. Disconnect your PC from your wireless hub, or unplug your broadband connection (or even quicker - just unplug your hub).
3. Install the new version of AVG
4. Reconnect to the Net.
Whilst you're performing the installation, you can be sure that your PC is protected, because you're not connected.
Also, you're wise to chose Girefox as your web browser - it has far fewer malware/viruses/spyware written for it, because of its relative (to Internet Explorer) unpopularity.