Replacing the motherboard outside warranty conditions invalidates the license.
You will probably have to purchase a new copy of Windows.
YOu could however try downloading the SP1 Refresh ISO file for your edition of Windows form the links here...
http://www.heidoc.net/joomla/technology-science/microsoft
once downloaded, burn the disk from it and use that otgether with the Key from your COA sticker to reinstall the system. You may need to activate by phone.
Noel Paton | Nil Carborundum Illegitemi |
CrashFixPC | The Three-toed Sloth