EndNote Basic is a web-based citation manager which allows you to have an online copy of your EndNote library. You must first create an account, through the Web of Science database. Click on the EndNote link at the top of the page and register.
You will then be able to transfer references from your desktop to your online EndNote Basic library and from EndNote Basic to your desktop. It is also possible to share groups of references with other EndNote Basic users.
To create a back-up file: Menu file -> Compressed Library (.enlx).
You can then save it where you wish.
Double-click on the .enlx file to open the compressed library.