Here is a compiled list from a LinuxQuestion posting (will be update accordingly):
6. Surf the internet, download files, pick up email without fear of the computer becoming infected with viruses, malware, etc. Linux - yes. Windows - it is possible to run as limited user which can limit malmare, but from my experience, it is difficult to use a Windows system as a limited user, and most people probably don't.
5. Ressurect old computer and use it as firewall, server, etc....