This is the Window Mode d3d9.dll I use for NFSUC:
ftp://64.89.144.81/public/upload/UC/m_nfsuc_win.rarJust copy d3d9.dll and d3d9.ini to your root NFSUC folder. Set window mode on/off in d3d9.ini ( 0 or 1)
EDIT: It works well but has one small bug. If you change your graphics settings while running in a window the game reverts to fullscreen. Save your settings and restart to run in window mode with your new settings.