When Windows 8 rolled out, in included a new feature built into the UEFI bios (now the standard for BIOS across all manufacturers) that locked the product key for Windows to that specific motherboard. One thing about this is if the motherboard it is tied to becomes damaged and is replaced by a MOBO of the exact same make and model (ie Hp Angelica 2 to Hp Angelica 2), the computer would boot up and work. Because you aren't using the same exact motherboard, then the recovery disk for windows from Dell will not work as a product key will not be detected and the signature left by the Dell mobo won't be detected either. The cost for a new windows license isn't much, $95 to $100, which is a real decent price compared to what it could possibly sell for IMO.
Reason for edit: Quick grammer correction and left one detail out that would have caused some confusion