Microsoft offers a cloud storage service called SkyDrive. If you already have a SkyDrive account you had 25GB of free storage space, but you better "opt-in" to keep it, otherwise you will lose it. For new users who didn't already have an account will get 7GB free storage, and can opt to buy more space if needed.
Microsoft recently added a new feature to this service allows you to use Windows Explorer to access the file in your SkyDrive account on your local computer. You need to install the SkyDrive client on your machine and it will create a folder (located in the Users\<your user name>\SkyDrive path) on your PC that is automatically synced with the SkyDrive service in the cloud.