Keep your files, backup and sync'ing together and simple using Skydrive Desktop App for Windows
which offers 7gb free cloud storage for each Windows Live/Hotmail ID and sells more for cheap.
It can be as easy as dragging anything you want backed up into its folder which lives both on your HD and in the cloud. But with a few more minutes configuration you'll have your files stored in the cloud ready to access on the internet and
sync'd to any of your devices.
After trying several methods for over a year I've settled on physically moving the active User folders to the Skydrive folder with the steps in User Folders - Change Default Location
You can also place the Skydrive folder on any other HD, but be aware that if it is moved from C and you use Windows 7 Backup Imaging it will force the inclusion of the data drive to which Skydrive and/or User folders are moved since they are System folders.
You can do the same on all your PC's and have one master set of files hosted and kept Sync'd this way by Skydrive, even access them from any device anywhere via the internet, share them publicly, by invitation, or link.
In using this method the only risk is if you'd delete a file or folder and have it sync on other devices before you realize you still need it. In this case the file/folder will be in each Recycle Bin.
An easy way to provide a backup archive is to use SyncToy
to regularly back up all of the User folders externally, to another HD, and/or to another Skydrive "Backup" folder, using Schedule SyncToy to Run Automatically With Task Scheduler in Windows 7 - How-To Geek.
I have it do this twice a week, choosing the "Contribute" method which updates everything that's changed but doesn't delete anything so that its a full archive.
If you prefer not to move the User folders into Skydrive folder, you can also copy each one there, delete the content in the C: User folder, then rightclick each User folder in Skydrive to add it to the related Library - Include a Folder - Windows 7 Forums.
If you use this Library method, keep each empty C: User folder in the Library so you can visually monitor if any files land there and simply drag them over to the Skydrive User folder. You may want to leave some files which exceed the Skydrive size limit in C: user folder so they don't cause an oversize error message.
See also: SyncToy - Backup User Data