Is it possible to run 2 anti virus programs at the same time on the same computer?

While it is "possible" it is NEVER advised as they both use the same calls to a portion of Windows and you will notice a severe slow down on your computer if running two at the same time. No need for two.

Other recommendations in this thread are good. All the name brand ones are good as AV software has matured a lot over the years. Spyware/Adware software isn't to that maturity level quite yet, so I can tell you in the industry we still utilize separate products (and sometimes mulitples of spyware products) to clean machines.

BTW AVG free for my home computer, I wouldnt touch Symantec's home products as they are severe resource hogs (although they will keep you clean). Symantec/Norton corporate products are much leaner than the home products you buy in the big box stores.