My solution to the imaging problem is simple. A reformat job always includes a new hard drive. A replacement hard drive is usually less than $60, which is far less than the cost of your time to figure out where someone has scattered all their files and made sure they're backed up.

I pull the old drive, pop the new one in, install windows (yes, install disks are a pain - I keep ISOs of the magical dell install disks that don't need activation, and am sad if I encounter non-dell hardware) and put their old drive in a USB enclosure and copy things over.

Usually I'll say to keep the old drive for a few months, and the next time I'm back we can format it and set it up as a backup drive.

The cost effectiveness of doing this is debatable - it takes a long time to do it right - find drivers, reinstall programs, copy data and then verify everything's working. These days I only do it for close friends and family members, and even then I've stopped hesitating to tell them they need a new computer.