Seems you entered an OEM SLP key on a non brand MOBO (ie. using a DELL SLP key to try and activate a non Dell MOBO !) -- the major OEM builders use a different type of activation where they use the same key for all of their systems and have specific code added to their MOBO BIOS that is read during activation and your MOBO does not have the correct code on the MOBO BIOS so you are getting that error.
How did you get the key you are changing it to (ie. software key reader, COA sticker on the system case or in the purchase of the product) -- If you used a software key reader on an already installed OEM system and it was factory loaded you will be using the SLP key which will not activate without the correct bios. There should be a COA sticker on the system case with a key that you should be using instead (they place the sticker on the case but it is not used unless you install using software other than their factory restore\recovery disk. So you should be using the key from that sticker not one read from the previous install (though technically if you changed MOBOs the old OEM license is not transferable to a new MOBO as that is considered a new system and needs a new license - but MS is usually flexible about giving you an activation code if the old mOBO died or became unuseable and the software is only being used on the new system.)