Reporting back. Flashed successfully using DOS USB pen drive. BSOD upon Windows boot with message "...BIOS not ACPI compliant...". BTW tried to patch the BIOS myself with the method you suggest (used PhonexTool 1.59) - it fails with the same "not reintegrated" error. Thanks!
I'm not too sure either, as I mentioned I used Phoenix Tool to mod. Andy may be able to explain the difference.
Well, I decided to take the risk, and it worked just great! Was able to flash the modded BIOS successfully from DOS. Then activated without any trouble.