use google chrome, dont run any executables or even open files that you dont trust, keep your software up to date, use updated third party software for everything, image viewing, music playing, everything. disable all network servers.

security is one of those things, they need an attack vector. if you aren't running any network servers, that means malicious code has to be executed by you directly, or by exploiting a flaw in a program by opening a malformed file.

you'll be fine. hell i have internet connected windows 98 machines at work still.