I have a PC running Windows XP 32 bit that's been unused since January and am planning to use it for some legacy gaming but also intend to set it up to dual boot with Linux Mint 17 Mate. What I'm wondering is how risky would it be to have the machine connected to the internet? Would XP only be at threat visiting infected web pages? Would it be safe to play online games like Guild Wars? Maybe visit major websites like Wikipedia and national newspapers? Or is setting the firewall to block all traffic the safest thing to do?

Linux is pretty secure, but you'd want a decent antivirus for Windows. Online games and major websites are safe, just think twice before clicking a porm link.