Dicho, there are all sorts of ways but some are straightforwardly reported by a browser and others to the best of my knowledge involve hacking techniques. You may like to visit http://scan.sygate.com/probe.html and see what this test yeids. In my case, without my firewall running, it can find my computer name is Jon almost instantly but with the firewall running, it can't get that info, so it's not information my browser is giving out.

You may also like to look at some of the bits I can pick up that are sent via HTTP. I've put a small ASP script at http://www.jonbanjo.com/me.asp.

Jon