It's just a difference in voltages and wattage. The mobile version of the P4 sips power to reduce heat issues. The cheapest mobile proc I can find is this one:
http://www.zipzoomfly.com/jsp/ProductDetail.jsp?ProductCode=86116

Please ask your computer's manufacturer if you can upgrade to this proc. Please ignore any warnings about voiding your warranty. I assume it is gone since you opened it anyway.