Windows Live OneCare makes it simple to back up your files to an external hard drive. The new version of OneCare allows backups to be updated automatically, every day or every week. If those backup files outgrow the external hard drive, you’ll need these tips to help start the backup process over.

Here’s some background. Behind the scenes, OneCare creates a series of .ZIP files with copies of your data. You’re not meant to use those files directly; if you need to restore a file that was accidentally deleted, open OneCare and use its Restore feature.

The backup files grow in size continually. After you’ve done a full backup, subsequent backups only copy files that have changed, but it appears there are two exceptions.

• If you delete a file from your hard drive and then do a OneCare backup, OneCare does not remove that file from the backup store; you could still restore it later.
• If you change a file, OneCare adds the changed version to the backup store but it does not remove the earlier version; when you use OneCare to restore the file, you can choose from multiple versions of the file.

As a result, it’s possible for the OneCare backup files to fill up an external hard drive. OneCare does not help you manage those files, although it’s an issue that will probably be addressed in an update eventually. The files are protected against erasure – if you open My Computer and try to delete them, you’ll get an “access denied” message – so it’s not obvious how to clear the drive and start over again.

There are two options. The first one usually works: sharing the backup folder resets the permissions so the folder can be deleted.

• Open My Computer and click on the external hard drive.
• Right-click on the folder named Windows OneCare Backup and click on Properties.
• Your goal is to share the folder and give network users the ability to change the files in the folder. Look for a Sharing tab or a checkbox.
• Close the Properties window. You should now be able to delete the backup folder manually.

The second one will work, but requires more care: reformat the external hard drive.

• Open Control Panel / Administrative Tools / Computer Management.
• Click on Storage / Disk Management.
• Right-click on the external hard drive and click on Format. (Double-check to make sure you’re clicking on the correct drive!) Check the box for a quick format and wait for the display to show you that the format is complete.

In each case, immediately start OneCare and do a full backup. It will remember your previous settings for additional folders and backup frequency.

OBLIGATORY WARNING: If anything is stored on the external hard drive besides OneCare backup files, do not format the drive. Let’s not have any silly mistakes.