If you don't have an antivirus program installed at home you must get one. AVG Antivirus a terrfic program available in a free version, so there's no excuse now! BTW, Microsoft Security Essentials is also free and a very good option. I have used both and they are quite solid. Not as good as ESET in terms of performance, however.
Here is a nice video that compares AVG and Microsoft Security Essentials: