Thanks very much opt_step, it worked perfectly. I've noted down the correct process this time so hopefully next time will be less confusing and stressful!
You have flashed the mod from pure DOS or Windows ? (I have modified QAT1x140.BIN) 1. Enter to the BIOS and set all options to Default 2. Flash your original (non modified) bios and check system stability
1. Modified bios was flashed from pure dos and from Windows. There is no difference. 2. I already flashed to origininal bios. Now windows boot normally.