So I recently shut down my computer so I could move it to a lower position (it's a desktop). Anyway, after starting it up again, I went to launch Halo and it told me it couldn't find some save game/profile data in 'C:/Users/Daniel/My Documents'. So I navigated to my user folder, and my 'My Documents' folder was no longer there... A day or two before this I did change a few registry settings, two involved changing the 'Program Files' and 'Program Files (x86)' folders from my SSD (C:/) to my HDD (D:/). And I had myself thinking I might've changed the user folder locations too, and that this might've caused the problem. However, something triggered in my memory suddenly, and I actually don't recall modiying user folder locations, so that's out of the list of culprits.

I first tried doing a system restore, to no avail. I then tried creating a new user account, and then copying the Documents folder over from there. But that didn't work, windows still treated it as a normal folder (the personal folders in 'C:/Users/<name>' have unique changeable properties unlike ordinary folders). I ended up trying to follow this tutorial, User Folders - Restore Default Location - Windows 7 Forums, and I can't get past step 25. It says I have to enter "shell:Personal" into the run dialogue, which I do, but I get an error saying "This file does not have a program associated with it for performing this action. Please install a program or, if one is already installed, create an association in the Default Programs control panel."