[0.4.13-dev] FreeLoader failure after installation on FAT filesystem (when using a small partition only)

Recent ReactOS daily builds will fail to boot after completing the OS installation from hard disk on FAT filesystems.

Steps

1. Start a new virtual machine with a clean hard disk image and a recent ReactOS boot CD.
2. Install the operating system as normal using default settings; make sure to format the installation partition as FAT (quick or full format).
3. The machine will restart correctly, taking you to the configuration wizard.
4. Complete the wizard using default settings, with any name and administrator password.
5. After finishing, the computer will restart. FreeLoader will display its boot menu. Both the "ReactOS" and "ReactOS (Debug)" options lead to a crash, rendering the system unbootable.

Note: The issue only happens with the FAT filesystem. Installing the operating system on a BTRFS partition will allow the virtual machine to boot.

Note 2: FreeLoader has an "Unknown operating system" entry at this point, which simply does nothing when used. This option is not present following a BTRFS installation.

Tested ReactOS builds

1. 3a207cd (MSVC)
2. 927e1d0 (MSVC)
3. e1e6cfd (GCC)
4. f86360f (GCC)

Debugging

The serial output file seems to have nothing very useful, with no error.
You may find the VGA screen dump and the serial dump attached.