How do I synch my calendars?

I use Windows Live, and I have two separate calendars, one online attached to my Hotmail account, and one standalone one on my desktop. They are both called “Windows Live Calendar”. How do I synch them? The menu option “Synch” is greyed out. “Synch all” does nothing. If I pick “Publish” it asks me for “Location to publish” and gives http://servername/webdav as an example, but this means nothing to me.

(Please don’t suggest I switch to google or something else instead. I have too much in these calendars to faff around re-entering it into another system, and I wouldn’t use Google if it was the last web app left on earth).