Dell M6600 change motherboard serial number

[RafalPL]

Hello.
Anyone know how to change serial number in dell m6600?
I desoldered SPI chips from motherboard and dump bios files.
After that i edited files in HEX editor and there I changed SN.
Next I installed SPI chips with edited bios on motherboard.
However, after opening windows, it turned out that the serial number remained the same.
Can anyone help me?