This page

https://www.grc.com/x/ne.dll?bh0bkyd2

from Gibson Research (the people behind spin write for those who remember it)

will check your system and tell you what it's saying about you (including if you are broadcasting your netbios name or not)

Unless you used your social security number as your computer name, I really don't think there's much risk in people knowing you call your computer red notebook or whatever though.