When formatting a Windows computer I always copy the full content of the harddisk to an external drive using an USB-based Linux distro (currently Knoppix). This makes sure that I can always retrieve any and all files in case the user suddenly realizes that they 'forgot' that one important file in the root of their C:-drive - which has a tendency to happen.
The laptop I'm currently working on displays an odd problem: in Windows, the disk space is reported as 220GB in use out of 260GB (NTFS, uncompressed) but it completely filled up a 320GB drive (NTFS, uncompressed, same cluster size) and still wasn't done copying. Using a different external drive with 220GB available I tried to copy the /Users directory which was reported by Windows as 120GB in size but completely filled up the drive taking up 220GB and still returning 'No disk space available' errors.
I've done this kind of operation a lot in the past but this is the first time I encountered something like this and I'm baffled by it. What would cause this to happen?
Edit: When working with malware-infested, spyware loaded systems that are beyond redeeming the last thing you want to do is start copying from the infected OS. I learned a long time ago that it'll just crash or lock up on you and that's why I use a USB-based Linux. Plus, I can just hit copy and leave it on overnight, no Windows nagging about files being in use.
Copying to an external NTFS drive means I can plug that drive back into the re-installed (vanilla) Windows and copy back the essential files to the computer.
Edit 2: the solution to my problem is simply 'use the right tool'. Apparently the regular copy of the Linux I used gets confused over NTFS and hardlinks. I used ntfsclone to copy and that worked like a charm.