1) Antivirus solutions do not co-exist - and not just the resident portion. I'd love to run a second or 3rd scanner like I can for spyware but Antivirus vendors have created a market that is use to the worst kind of lock in. Why can't I run 3 different products side by side and decide which one's resident scanner I want switched on? I'm sure there are technical issue but I'm also sure they're not insurmountable.
I decided on one paranoid night to try to do just that. I found that for the most popular free solutions (AVG, Avast, Avira) you can install them side-by-side and narrowed it down to just one resident scanner running. You either have to find the hidden option in the menus, disable the start-up entries, or just opt not to install them during setup. I was able to safely ignore the warnings about having other AV products installed during the various setups.
An easy solution for individual files is VirusTotal. You can upload the file (less than 20MB) and have it scan it with ~39 different antivirus programs.
The most important thing to remember is that security is a process, and not a product. (If I remember that saying right... and I don't mean explorer.exe)
We’re going away. Pack your shit, folks. We’re going away. And we won’t leave much of a trace, either. Thank God for that. Maybe a little styrofoam. Maybe. A little styrofoam. The planet’ll be here and we’ll be long gone. Just another failed mutation. Just another closed-end biological mistake. An evolutionary cul-de-sac. The planet’ll shake us off like a bad case of fleas. A surface nuisance.
A long time in the future, from a George Carlin far, far away on the planet Liked-Their-Coffee-Way-Too-Much
"Consider a spherical bear, in simple harmonic motion..." -- Professor in the UCB physics department