Hello jackcone! Welcome to the Windows 7 Forums.
Sorry to burst your bubble, but ANY TIME you change out a motherboard, you MUST do a clean or custom install. No exceptions. Sometimes it's even necessary if you do a BIOS firmware update.
It's especially important if there are different chipsets; North bridge and South bridge chips, audio chipsets, etc.
The only time there is an exception would be if you were replacing the motherboard with an exact same model and make of motherboard.
What brand and model did you replace? What is your motherboard brand and model?
Give us some information, please.