As long as you save it as backward compatible, I don't see any problem.

 I am doing a school project and  I have 2007 software on my computer, planned
 to do the project on that, but would I be able to show it on a 2003 software.
 Is it backwards compatible?

Save the file normally, using Office Button | Save. This saves the file in
2007 format, to make it easy for you to continue to edit.

Then choose Office Button and hover over Save As. A flyout menu will open to
the right. Choose PPT 97-2003 Presentation. You'll be able to show that one
on the 2003 system.