It's not that hard to hack someone with just an IP Address...
Yes, yes it is.
Every website you visit on the Internet? They know your IP address.
Every gaming server you connect to? They know your IP address.
Everyone you directly connect to in any game? They know your IP address. (Some match-based games do this automatically, without your knowledge.)
Now, a naked Windows setup on the Internet is, frankly,
fucking stupid, regardless of what you do. If, for whatever reason, you haven't properly patched up security holes... If someone doesn't specifically get you, a virus or worm
will. Get yourself behind a security router of some sort, or behind a firewall.