I wiped my MAC adress , so I can't find it anymore in ipconfig /all.
After BIOS flash with FPT.exe your MAC will go to 88 88 88 87 88.
But everything worked for me, even with the "wrong" MAC adress.
So you could also just flash with FPT.exe and leave it like that.
But you can hex edit the BIOS rom, with a hex editor, you need to find the 88 88 88 87 88 part and replace it with the MAC adress you want.
Best way to do it,
Find your original MAC adress. And save it somewhere.
Download the F4 BIOS rom, edit the 88 88 88 87 88 part to the MAC adress you want.
Save the ROM in the hex editor.
Flash the rom with FTP.exe -f bios.bin (any filename will do)
Then flash the BIOS again with Q-Flash, with an unedited ROM. (so you need 2 ROM files, one edited, one unedited.)
I don't know if the last step is necessary, the part where you flash an unedited ROM again.
I did this to be sure, the BIOS is flashed correctly.
But be careful, one wrong digit with hex editing might brick the BIOS.