Could it be failing when it reaches a particular file?
A number of windoze files are locked by the OS so a simple drive copy always fails.
Also if the destination partition is FAT32 rather than NTFS, it will fail on the first file which is bigger than 4GB.
Best way is Trueimage, IF the source runs windoze. I have used it for years, and routinely backup a laptop with ~ 30GB of stuff on it, over a LAN, to an ethernet connected network drive, or another PC. The resulting image file is say 20GB. But like I say the destination drive must be NTFS not FAT32.