>>21 How could you possibly find a virus?
The only time you see a problem is when it's too late.
It's not a program.
It's not installed on your system.
It could be in an archive.
It could even be a file without an extension.
You can sometimes get spyware (like Conduit), but manually finding and deleting viruses is almost impossible.
I would say its just worth it to get a free anti-virus. AVG free is a good one.