[reboot]

For those of you "in the dark", there are only a couple of ways you can get a virus or trojan.
First, it must be an executable file of some sort, not just .exe but things that masquerade as .scr .jpg .gif .avi .mpg may NOT really be what they purport to be.
You need to "see" the WHOLE filename to be sure what it is.
A couple of ways to do that:
Open a DOS box, and do a "dir" on the folder that contains the questionable attachment/file, is the easiest.
If it ends in .vbs or .exe (the filename may be something like brittneyspears.jpg when viewed in Outlook, but in DOS, it's brittneyspears.jpg.vbs or brittneyspears.avi.exe), it's time to get suspicious.
One can also "bury" and executable in HTML code, but that's a whole 'nother topic.
There ARE good files that end in .vbs (my little freemem prog is one), but the infamous Melissa is also a .vbs script.