It may big issue to open the Microsoft 2007 files in microsoft 2003. But it is easy to open the file in Ms 2003. You have to download the MS2007 compatibility pack for Ms2003.
Download it from here:
http://www.microsoft.com/downloads/details.aspx?FamilyId=941b3470-3ae9-4aee-8f43-c6bb74cd1466&displaylang=en
Enjoy...!!!
Suggestion:
Better start to use Ms 2007.
Old is gold but New is
Open Microsoft 2007 file in Microsoft 2003 -Computer Tricks
Comments