I have to admit to not doing much homework on the subject but I got a call from a friend last night who needed help. Small company, field Salesman had XP and was VPN'ing in.(don't know what they have). Now he bought a Laptop with Win7 and it dows not work. I understand the client parts that are explained here. My queston is on the Corp Office side, what VPN server/appliances are good and cost effective for whatever Windows client and works with Windows ADS too? I will not be offended if you tell me to "go check these sites" but I was trying to help a friend.
If you won't be collaborating online regularly (and even if you are), I'd suggest you consider services like dropbox.com or even cl1p.net. A VPN is only worth your time if you're managing lots of computers around the world, and want them to quickly communicate with each other.