How do I get rid of XP Security virus if I can't get on the net?

There's a rouge virus out there call Windows XP Security 2011 (2012) and I have it on my laptop. I only have it on there because my anti-virus expired and I didn't know it. I know a good program to remove it, trouble is I'd have to download it but with this virus I can't get on my internet. What do I do? I can't afford to take it to a professional. I'll be on my family computer hoping to get lots of good answers.