Another test...
This morning I used Macrium to create an image of the C: drive (Samsung 830) onto an external usb hard drive. I then moved the external hard drive to an older pc (Dell GX240 running XP Pro). The copy of Macrium installed on the Dell had no issue verifying my image, I ran verification twice and it passed both times. I am beginning to wonder if this is an issue with Macrium or with Windows 7 64 itself. Here's an excerpt from the Macrium Knowledge base (
Understanding Image Verification Failures (Verification))...
"When an image is created each block of data (generally 64K but may be larger depending on the partition size) has an MD5 hash created after it is read from the disk and before it is written to the image file. This hash value is saved in the index of the image file. When the file is read back the hash value is recalculated and compared with the original hash in the index. Any discrepancy between the two values indicates that the image file is corrupt or cannot be read back reliably."
If I am understanding this correctly, the verification process reads each individual block within the image file, calculates the MD5 hash and compares it with the original MD5 hash that is stored within the index section of the image file. So if this is how it works it makes it look like Win 7 64 was able to calculate the MD5 from the original file correctly during the imaging process but for some reason cannot create a corresponding MD5 during the verification.
I'm not ruling hardware out yet but am keeping an open mind and looking for clues. My thanks to those who have replied and thanks in advance to anyone who can shed further light on this issue!