Originally Posted by Brutha
Probably it is enough just to install a Firewall
Better yet, use an external firewall. If your PC is
compromised then any software on it can be compromised or fed fictitious data.
If you have a spare old PC lying around you can turn it into a dedicated firewall box using free software called "smoothwall". Alternately you can buy a hardware one.
Even if your PC isn't currently compromised it's still good to have external firewall software so a virus or something can't disable your firewall.
All that said, I agree that the risk is minimal if you reinstall the OS (especially if you take the opportunity to install Linux instead