I've got an Edimax little USB wifi device, not that one, but a similar one. Looks like yours uses a
8188CUS chipset, so how about downloading the drivers straight from
Realtek?
And ya, Comcast sends us letters every once in a while saying we're infected with a bot or something, but I use MSE and MWB on all my computers, and haven't had any issues. I would also recommend Avast or Avira. Most of the time when we get a computer with a virus at work, it's cuz something like Java is ridiculously old and outdated. Do yourself a favor and go to
Ninite, and select all the programs you'd like to use. Download and run, but keep the file, as it's great for running once a week (or month, if you're lazy) and keeping everything up to date. If nothing else, use it for an easier Java updater. Then go into Control Panel, and Uninstall Java 6 (You can leave Java 7). Most people don't know this, but it makes a HUGE difference.