Backup files are usually the first thing to go when you run out of space on your backup storage device. You presume that it is ok to delete certain files and later realize that you have made a dreadful mistake.

How do you know which files you can safely delete? Follow these simple rules and you’ll never delete backup files you might need later.

Backup Files To Permanent Media

Before you delete your backup files, have you considered making a copy to permanent media such as CDs or DVDs? Putting your backup files on this sort of removable media is convenient and cheap for small amounts of data.
One of the best things about CDs and DVDs is that you can store them off-site so that you still have backup copies if your house or office burns down. I prefer to keep my disc backups in a safe deposit box at the bank where I know they’ll stay secure from almost any catastrophe.

Putting your backup files on disc couldn’t be simpler either: just insert the blank disc, drag files to the appropriate folder, and click Burn. Wait for the burn to finish, remove the disc, put it back in, make sure the files burned correctly, and then you can safely delete the backup files off your disk drive.

Save Backup Files In The Cloud

The main problem with disc backups is that they’re annoying. They require you do work—you have to buy discs, you have to burn your backup files, you ought to check them, and you have to store them in a secure place.
Cloud-based backups eliminate all that hassle. You sign up once for a service like Mozy. Then you just need to tell them where to find your backup files. They put your backup files on their cloud server and keep them safe.

Unnecessary Backup Files

Some backup files are unnecessary—as long as you expect your computer to keep working. For example, several programs create copies of the files they work on with a .bak file extension. These files can almost always be safely deleted. Other programs create longer-term backup files. For example, my accounting program creates .log files which store a list of every transaction I enter—that way I can quickly re-enter transactions if I forget to save my file.

There’s no easy way to find all of these little backup files created by all sorts of different programs, but you can follow these steps:

  • Look for old files (use the detail view in Windows Explorer to check the file modification dates).
  • Verify the files aren’t necessary by saving all of your data, exiting all programs except Windows Explorer, and moving the file to a different directory (not the Recycle Bin).
  • Open your usual applications and files. See if you get any warning messages. If you do have problems, move the file back to its original location.
  • (Optional.) Wait a week and see if anything breaks. This simple test separates non-essential backup files from essential system files.

If nothing goes wrong, you can probably safely delete the backup files—although I still suggest you save them on permanent media or on a Web-based service.


Always be aware of what the important backup files are on your computer and you will never have a problem.

Backup files are easy to delete in a pinch, but you must remember that they exist for a different kind of pinch. Because they could be the only way to get your data back, be extra careful before you delete any backup files.