Hello wxford and welcome to Seven Forums.
Are you trying to create a System Backup Image of the OS, or are you trying to backup personal data?
Imaging is not the best or recommended method to backup personal data.
Imaging is the recommended method to backup the OS partition(s).
I'm guessing you want to create a System Backup Image.
Run a System File Check to see if any errors are found. SFC /SCANNOW Command - System File Checker
If you already haven't, you can do a Google search for 0x8007045D
and see what you find.
Here's a couple links i found that may help. 0x8007045d Error message when you try to perform a full backup on a Windows Vista-based computer: "The request could not be performed because of an I/O device error"
If you don't find a solution, you could consider trying a different program to create backup images.
Macrium Reflect has a free version that is recommended by many here on SF. Macrium Reflect FREE Edition - Information and download
You can also get a free version of Acronis from the Seagate website.
Seagate and Western Digital have a free version of Acronis for anyone that has one of their HD's.
Macrium, Acronis, and other programs are better and much easier to use than Windows backup imho.
I use and prefer Acronis (paid) for Backup Images because I've used it for many years without issues.
hope this helps,