I downloaded Windows 8 a couple days ago. I tried creating a system image to a 500 GB (409 GB free) Western Digital external drive four times and each time after several minutes a message said that the backup failed. The Recover Partition backup seemed to complete OK each time. The failures occurred after a minute or so into the OS C: drive backup.
The external drive checked out OK. The drive previously had a system image for Windows 7 that was deleted before the backup attempt. Here are 2 of the messages I received as the backups failed. The other 2 were about the same, I think.
"There was a failure in preparing the backup image of one of the volumes in the backup set. (0X807800C).
The mounted backup volume is inaccessible. Please retry the operation. (0X8078004F)."
"There was a failure in preparing the backup image of one of the volumes in the backup set. (0X807800C).
The specified disk cannot be found. (0X80780081)"
Below were the 2 files on the external drive after the failure. I guess the first was the completed Recovery Partition backup. I don't know much about this sort of thing.
7da23344-ab79-11e1-887d-806e6f6e6963.vhdx - 7.61 GB
7da23345-ab79-11e1-887d-806e6f6e6963.vhdx - 7.00 MB

Does anyone have any ideas about the problem? The only virus software on the PC is Windows Defender that came with the OS.