Step By Step - To Change Permissions of the directory and all of its contents:
1: Open Explorer.
2: Browse to the directory in question.
3: Right-Click Offending folder.
4: Click Properties
5: Click Security Tab
6: Click Advanced
7: Below the 'Permission Entries' box, click 'Add'
8: At the top of the new window, click 'Select a principal'
9: Type the local account name, or the email address of the relevant Microsoft Account, into the field below 'Enter the object name to select'.
9a: Click 'Check Names' and confirm what appears in that field matches the account name in question.
10: Click 'OK'.
11: Check the relevant boxes under Basic Permissions. Also, click 'Show Advanced Permissions' and check the additional relevant boxes.
11a: Do NOT think that ticking the 'Take Ownership' advanced permissions checkbox will propagate ownership of the directory and all of its files and subdirectories. I just tested this while writing this answer. It will not.
12: Click 'OK'.
13: Click the Check Box at the bottom of the window next to 'Replace all child object permission entries with inheritable permission entries from this object (This is the step I missed which led to much wringing of hands and gnashing of teeth).
14: Click 'Apply'. Click 'Yes' in the scary pop-up window that asks if you're sure, and wait. Depending on how dense the contents of the folder, you may be waiting a few minutes. Don't worry about if this f***s up permissions for other users, you can always go back and add the permissions of those other users later. Chances are it won't unless you removed them all from the parent directory, and chances are you're the only person using this computer anyway.
15: You're done. Congratulations. Move the folder, delete it, rename it, burn your house down for insurance money and use that money to get wasted celebrating, but probably not that last one.
To take ownership of the directory and every directory within.
1: Follow steps 1-6 as indicated above.
2: Click 'Change' next to the name of the current owner.
3: Follow steps 9-10 as indicated above.
4: Click the check-box underneath the new owner name next to 'Replace owner on subcontainers and objects'.
- Click 'Apply' and wait. Congratulations. All those folders and files are belong to whomever.
This is probably a horse so dead that its entire lineage is dust by this point, but here's hoping this helps someone, somewhere, sometime.