As far as I know, it's totally free. If you have an MSN or hotmail e-mail address, you already have a Windows Live ID.
It's totally free. You can use a email you already own, maybe @yahoo, or @gmail? Or you can register one with them. @live or @hotmail or @msn. Your choice
certain groups are looking to unify large parts of the internet under ids such as this. I know these things are necessary in some places and beneficial in many ways but please fight this and opt out when you can...all we need is an internet version of the SSID#...I'm not kidding.