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If I make a copy of EVERY single file on my hard drive, my programs won't work any more and I'll have to re-install them. This confuses me because the registry is stored on the hard drive, along with all windows files. If every file was copied, I don't understand why a re-install is needed.

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If you do a disk clone then you have copied everyfile (Including the registry and all versions of it) and it will work... – AthomSfere May 17 '14 at 21:40
There may still be issues with software which generates a signature based on the hardware it was originally installed on (Windows itself does this, at least for OEM licenses), and an attempt is made to run the program on a different set of hardware. – TwoD May 17 '14 at 23:02
What tool do you have that can copy -every- file on a windows file system? This could certainly not be done within windows (certain files are locked while the system is up) and would need a specialized boot disk to do this. By this stage it is likely easier just to make a disk image anyway. What tool are you using? It is likely this tool is not indeed copying every single file. – Vality May 18 '14 at 4:34
@Vality I've never done it, I'm just asking because as a general rule I (thought) I knew that you have to re-install stuff. – Frank May 18 '14 at 4:35
@Chipperyman Ah, I see. Well if you do have a tool that can copy every file it should work, however actually doing this is very difficult, particularly as the windows boot-loader uses a supposed ntfs partition which does not actually comply to ntfs so normal copying tools will fail there. There are also a special set of system files and a swap file which will likely not copy cleanly. Finally adding the point of the other answerers here I would say as a general rule its a bad idea to copy a Windows install at file level, likely better off with a disk image, this will avoid the reinstalling too. – Vality May 18 '14 at 4:39
up vote 5 down vote accepted

If you did copy every single file in any hard drive, then you would have also copied your OS and, more importantly, your User files.

The Windows Registry can be understood as having two main parts: the part that every user in that machine has in common and the part every user has individually. If every file has been copied, then everything would run as well as it did on the previous machine1.

However, most times, users only backup the "Program Files" and what's on the "User's Documents" folder. These locations don't have the files that store the Registry entries associated with the programs stored in Program Files. Those locations can be found in this Wikipedia article.

The main problem here is that those programs may depend on whatever values there are in the current machine's registry and those values are created when installing the programs.

As such, if you did what most users do when they copy their hard drive, then you would need to reinstall the programs because, as stated, the registry entries that are needed for the programs to work don't come along.

1 - If the machines were also identical, in which case the drivers would also be.

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