We strongly recommend that you keep several backup copies of your critical computer files, especially your EndNote libraries and papers that you are writing. There are many ways that a file can be damaged: CDs and hard disks can fail, viruses can erase or corrupt files, and, of course, there is always human error and the possibility of accidentally throwing away your thesis or grant proposal the day before it is due. If you have any kind of disaster, big or little, backup copies can save you hours or days of work.
The simplest way to make a backup is to use the Macintosh Finder Windows Explorer or the Windows desktop to copy your files to a CD or other portable storage device. This will work for your EndNote libraries until they are too large to fit on one of these.
To backup larger files, or automate the backup process, use a backup program. Your operating system likely includes a backup program. There are also a number of commercial backup programs available that make regular backups easy and efficient; these programs can scan your disk for files that you designate as important, keep track of changes, and save you time by copying only the changed files. In addition, they can split large files, including EndNote libraries, among several disks. If you ever need those files, the backup program can "restore" them from the disks.
Keep at least two sets of backup disks, each at a different location. We recommend that you have sets for alternate days, so if you discover that something went wrong yesterday, you will have the day-before-yesterday’s version.
Make archival sets of the files listed above whenever you finish an important document. An archival set should include all of the files that are needed to recreate a final formatted paper. Label the backup disks, lock them and keep them in a safe place far away from your computer (preferably off-site). If you ever need to recreate the document, you will have all of the necessary files.
See Important Files to Backup for more information about this topic