The first thing to get is a good free ant-virus program. I like these listed here. among others. I trust these.

As far as free Anti virus programs go, these are some of the best ones that I have used.
I use Avast on my own computer.

Avast antiVirus

http://www.avast.com/index.html

I like this one, just because it is easy to use and is fairly fast.

It’s really important to protect your computer with Anti Virus.

Get AVG Free

http://free.avg.com/us-en/homepage.

So you mine as well do it for Free! I do and I like it!