I used a predecessor to SkyDrive called Windows Live Sync
(a.k.a Windows FolderShare), which just synced folders on different computers.
They came out with a new version in 2010 called Windows Live Mesh which didn't support Windows XP--fine, no big deal. But then they announced that the old version would stop working. No upgrade path. Microsoft didn't host your files, just an index of the files, so it couldn't be that expensive.
I still find it inexplicable, but I've learned my lesson. Don't trust Microsoft to continue to support old products.
It's a bit more complicated. Mesh predates SkyDrive (and Dropbox for that matter). It was in beta since before Vista, if I'm not mistaken. It was truly visionary product. Then something happened and it never got released properly, instead FolderShare or Live Sync came up, which was a far cry from the original vision. Mesh beta continued to exist. The Live Mesh release appeared in 2010: functionally it became closer to the original beta, but very toned down (did you know that there was an idea of "Mesh apps"?). And then SkyDrive started to gain steam and recently its app was released. This app dropped shared folder sync and remote desktop features. Mesh is and was a superset of both SkyDrive and Live Sync apps.
Live Mesh held so much promise that I am still a little disappointed that Microsoft decided to sunset it. Not only did it do what SkyDrive and Dropbox do today but it also did file and folder syncing, bookmark and application settings syncing along with Remote Desktop between shared machines. I think Live Mesh shutting down was one of the reasons why Ray Ozzie left MS.
They came out with a new version in 2010 called Windows Live Mesh which didn't support Windows XP--fine, no big deal. But then they announced that the old version would stop working. No upgrade path. Microsoft didn't host your files, just an index of the files, so it couldn't be that expensive.
I still find it inexplicable, but I've learned my lesson. Don't trust Microsoft to continue to support old products.