What's the difference between disk imaging and copying?

Hi Leo
A query on this article if I may. Can you still restore from a FileSystem image in the same way as you would with a 'full' Disk Image?
Thanks!

Leo, if I may respond to your questioner regarding restoring a file system image: There are two answers -
1: As long as (as Leo says) it includes all of the system information relating to the files and folders it copies as well as...boot sectors" then the answer is - Yes...however, you'll be overwriting everything on the drive to which you're copying the data.
Answer #2: If all of the data from the initial image is saved as a ginormous file (or several), then it would need to be restored by the program that made the image(s), or one built to restore such images.
Steve Burgess
Burgess Computer Forensics

Leo,
I’d like to add another layer of distinction, for I get asked this question myself - but in my field, they’re asking something (slightly) different although they don't always realize it. A “disk image” may be different from a “forensic disk image” due to the provable validitiy that the image or copy is identical to the original. Several computer forensic packages verify this by generating a hash value (or hash signature) for the original and for the copy, and then comparing the two. If they match, they’re identical (well, the odds are better than a quadrillion to one that they’re identical). A hash is a number calculated form string of text – in this case, the string of text is every consecutive sector on the hard disk. If it is if value to your readers, we’ve put up a glossary of such terms here: http://www.burgessforensics.com/glossary.php

Leo,
I presume that your two types of imaging are distinct from cloning or making an exact copy of the disk as offered by Norton Ghost and Acronis True Image? Thanks.

Message to Steve Burgess.

Thank you very much for responding.

Leo explained very well the differences between the two backup mediums, but left me wondering whether you could restore in the same way once backed-up.

Again, thank you for the time taken to explain this to me. It was very a very detailed & informative answer.

Kind regards.

I guess both disk imaging and exact copying will be good enough for backing up files.
But, I'm sure once in a while a computer simply won't start due to reasons like hard disk crashes, improper use of registry cleanup, system maintenance/optimization, Anti-malware programs, deletion of infected system files, software uninstallation,etc. Then one could restore files from a backup copy. But how to restore anything if you can't even boot your computer? What if even your partitioning info is lost? This may turn out to be a real problem as even an exact copy might not be enough.
My solution has been:
Keep C: as small as possible, about 20 MB (use another drive for virtual memory - bettter in many ways),
Make an exact backup copy in a special partition (F:) in my second hard disk regularly, including all software and hardware system files.
Thus, if anything goes wrong with C:, I start my PC again, select F: as the bootup drive in BIOS and boot again. After recovering any needed data on C: I do whatever is needed to make it boot drive again. In cases of drives other than C: same operation is easier. Of course, as in the other backup methods, some data and changes after last boot may be lost.
I guess this beats re-installing Windows , re-downloading and re-installing all the service packs and patches (I shudder when I think the time I had to spend to download multi-processor drivers, XP patches for the same, re-activation problems, license problems due to lost registry records,...), re-setting all the preferences not to mention other work needed.
Note that if C: crashes, system restore will probably not work anyway.
Keeping C: small and preferably keeping some of the system files elsewhere makes it easier and faster checking for malware, defragging and compacting the operating system as well as keeping boot-up and turn-off times lower.