Small suggestion from my side - maybe it would be good to prepare OVF package with ready to use system for VM testing ( https://en.wikipedia.org/wiki/Open_Virtualization_Format ) Same way is distributed Kali linux https://www.offensive-security.com/kali-linux-vm-vmware-virtualbox-hyperv-image-downlo...

VirtualBox: Version 5.1.28 r117968 (Qt5.6.2) Virtual Box configuration (Session Information) OS Type Windows 2003 (32-bit) Base Memory 1024 Processor(s) 1 Execution Cap 100 Boot Order Floppy, Optical, Hard Disk VT-x/AMD-V Disabled Nested Paging Enabled Paravirtualization Interface Default Display Vi...

So there was no forced reboot - and tried 3 times to install ReactOS and all failed same way.
Now I have 2 options:
1) find tool which is capable to repair offline registry hive on FAT partition.
2) debug installation process to find out what&why corrupted registry

I've done an installation on VBox according to https://www.reactos.org/wiki/VirtualBox directions. Taken all default steps, and receive BSOD after second restart. Maybe it would be easier to understand if I attach screenshots from VBox, but until then the error is Verify Hive Header failed: ... Sequ...