Does not like the situation it is in. You more than likely will need to do a "repair install" since you replaced the motherboard, unless you had the same model and make before. Just boot to the Windows XP disk and do the install from the screen after the software finds the established install and asks if you what to do the repair or reformat. You can then install the motherboard drives after the repair is completed. Do not use the first screen repair or you get the recovery console. Hopefully you do not have an OEM version, as that will not allow the reinstall.
I am rebuilding my computer, the only things I have replaced are the motherboard and processor (motherboard = Intel