so what is the difference? Live Mesh gives you the possibility to sync files without restriction in the sum of size of all files. you can choose to sync files without using the online space. SkyDrive is the name of the online space, which is 5GB big. Syncing without using SkyDrive is only done when the systems (microsoft call it devices) are online at the same time. So if your systems are never online at the same time your files will never be synced. Keep in mind: Microsoft stopped support for Windows XP (Live Mesh Beta supported xp, but will shut down in 03/2011), but they support MacOSX (>10.5): http://explore.live.com/windows-live-2011-system-requirements If you chosse DropBox you are limited to the size of the online space, which is initial 2GB big. Advantage: you can sync with mobile devices and windows xp, linux, MacOS, Android, Blackbarry, Iphone, Ipad, ... And the best: There are free ressources for developer in multiple languages. https://www.dropbox.com/developers/releases