What is the internal structure of a Windows shortcut?

Question

3 HDD in one computer: 2 with Windows XP, 1 with Windows 7, sequentially load the operating system from each of them.

I discover that some working shortcuts (not all

Answer 1

Shortcut (.lnk) file format information can be found at [MS.Docs]: [MS-SHLLINK]: Shell Link (.LNK) Binary File Format.

However, to spare you from reading that whole .pdf, one thing that is stored within a shortcut for sure (can be checked by "looking" at the shortcut using a hex viewer) is the (full) target path that it references (!!!important!!! at creation time): so it's "DriveLetter:\the_full_path".

To clear up confusion, I'd suggest playing with shortcuts that have targets on the same drive.

When switching HDDs, the DriveLetters (aka "C:") point to different things:

• Let's say that you created on one of them a shortcut: "C:\shortcut.lnk" ("C:" is the DriveLetter assigned to the HDD where Win booted from): let's call this HDD1.
  The shortcut points to target file located on another HDD (and partition): let's call this HDD2 (e.g. "E:\target.txt)

• When you'll switch HDDs (making HDD2 primary boot disk) the DriveLetters will change too, so now:

  • HDD2 will be "C:"
  • HDD1 will be "D:"

  
  Things complicate even more when introducing HDD3 and so on.

As an answer to our question: the .lnk files don't work because their target is no longer present.