Error: KB2390372v2 does not apply, or is blocked by another condition on your computer.

When installing AX 2012, sometimes you might get the following error when applying KB2390372v2 (required by setup). 

KB2390372v2 does not apply, or is blocked by another condition on your computer.

This can be solved by installing the most recent setup support files for AX 2012. Run the appropriate Cumulative Update (CU) setup. Yes, this can be done even when AX isn't installed yet.

Restart setup and it shouldn't need this hotfix anymore.

Danish translation of error for those searching:
KB2390372v2 kan ikke anvendes eller er blokeret af andre tilstande på computeren