Can't run system image to the drive that I want

All of the sudden today system backup stopped recognizing my internal hard drive that I had previously used for backups . I can access this drive through regular methods so the system does see and allow access. I got the error code 0x81000002 which I can't find anywhere on the net. Can someone please help me out.

Bruce

Although it doesn't solve your problem, it's always best to use an external drive for backup purposes.

In answer to your query: Error code 0x8100002. Your last backup did not complete successfully. - Microsoft Answers

The internal drive that I was referring to is a backup only drive. I would love to know why, all of the sudden, this is happening.