MS Project 2007 to 2003 Converter

I have installed Microsoft Project 2003 on my system, Now whenever I open a Project file that was created in 2007. When I want to save it a "Help" screen opened recommending I download Service Pack 3 which would provide the required converters, So I followed the instruction and did it. Again I re opened the file of Project 2007 and again "Help" screen pops up recommending SP3 be installed when I try to save the file. In this service pack PC reboot instruction was not provided, but still I reboot my machine, to just to check whether the problem has been fixed, but it did not. Can you please help me with your suggestion.