Dump AVG. As of recently they're just hogging too much memory and missing too many major viruses to be of any use anymore--they're just trying to encompass everything and impeding their own performance. They used to be really good, but right now, I think you would be better off with a few different options (some of which you may already have).
1. Download and update
Malwarebytes. Run a full scan.
2. Download and install
Microsoft Security Essentials.
3. Download and install
Piriform CCleaner. Run it.
4. Download and install
Piriform Defraggler. Run it.
Try these four things before deciding to just wipe it all together. If those four don't get you back the performance you want, or the performance that can last you another month until you get a new computer, go ahead and wipe it. Just be sure to save everything you want.
I didn't once..
Cheers,
Kyle
[edit]
I also forgot
Spybot Search & Destroy. Download, update and run a scan with Spybot as well.