Windows 7 error code ox80070002 on backup

I recently upgraded from Windows Vista to Windows 7 Home Premium. When attempting to back up to an external hard drive with Windows back up in control panel it stops at about 20% completed and gives me the error code: 0x80070002. I have done a cmddsk /f/r on C drive. Didn't seem to help. I have a HP AMD quad with 8 gig of Ram and came with Vista home premium with free upgrade to windows 7 which I have done. Anybody know why i'm getting Windows 7 error code ox80070002 on backup? Any one knows what may be causing the error message? Kindly help me out. Thanks.

This issue may occur if there are duplicate accounts on the computer. This error could occur due to a number of reasons. Did you install Windows Vista and Windows 7 RC compatible Virtual PC or Windows XP Mode beta? The Administrator account is disabled by default in Windows 7? Have you taken any action to enable the (built-in) Administrator Account?

Unless the Administrator Account was enabled (and used) then those files would not exist on your machine. Find this key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList on your system. Then you need to right click on ProfileList, click Export, export it to Desktop as a backup. Then please check each sub-key, find the ProfileImagePath value, check if it points to a correct path. If not (or there is no such a value), delete the sub-key. After that you need to reboot and check the backup again.

If you configure backup to exclude those files then the error may disappear. If the CheckDisk is clear, you may want to try doing a System File scan by going to Start, All Programs, Accessories, right click the Command Prompt and choose Run as Administrator. You may be prompted to continue. In the Command Prompt type the following command and press enter: sfc /scannow. If you do not run the Administrator Account then it is probably safe (after saving a copy) to delete any folders found in C/Users that belong to the (built-in) Administrator Account (not any active user accounts), and to disable the account too.

If you are worried about data loss, you should be able to back up those files manually or at the very least, all of your documents and personal files, movies, etc. You can solve some computer problems by checking a drive or drives for errors. For example, you can check your computer's primary hard disk to fix some performance issues, or you can check an external hard drive if it's not working properly.