Sync files between Win7 64 desktop & laptop

I'm planning to buy my first ever laptop for a four week business trip. I'll buy it with Win 7 64, like my desktop, and will copy the contents of my desktop HD to the laptop before I leave.

When I return, I'll want to sync all changed files from the laptop back to the desktop again.

I feel a bit embarrassed to ask how to do this, as it's obviously a common issue ... but I've googled, browsed these forums, leafed through my copy of Windows 7 Inside Out -- and still can't find what I need to know:

What's the easiest and most trouble-free way of syncing these files?

Should I buy an Easy Transfer cable? Use a third party program, like Foldermatch or Laplink or Syncback Pro?

I understand that I can sync files with an online intermediary -- Windows Live, I think -- but I'd just as soon not go that route. My hope is that there's a cable I can get (like the Easy Transfer cable) and some simple software I can use or download that will do the job for me.

Thank you!