Help – Windows wont load!

I have a PC to fix for someone. The Mother board has a problem and has been replaced. Unfortunately this is of a different type and has more RAM – its own network card etc.

When I attempt to boot Windows XP I get a screen which says that windows did not start sucessfully and gives options for the type of load – none of these work. I can boot from the Windows XP CD – one of the options will allow me access to the windows directory on the disc to fix it! But I haven’t a clue how to – because I don’t know whats wrong!

By the way its an OEM version of XP Home.