windows 7:upgraded mobo, cant activate!

I purposely purchased windows 7 Retail, not OEM for this reason!

I had windows 7 pro installed on my computer with an older motherboard, i upgraded the motherboard, reinstalled 7 and when i went to activate it the activation wizard says “type a different key for activation-the product key you typed cannot be used to activate windows on this computer”

any help would be great!