Microsoft Word 2007....which format to save in?

I just got done spending a lot of time on a resume doent....when I went to save it I chose the Win 97-2003 style because I would ume more people these days have this version than newer versions...as soon as I saved the doent, the formatting got all screwed up. I had to reselect Word 2007 format from a drop down box and then it went back to the right way again. I then saved it as a Word 2007 doent. So now I have two versions of this resume. I need to email it to a prospective employer, but I don't know which one would be better to send them? I don't want to send them a version that's going to look screwy on their screen, and have them think I can't create a decent looking resume. What should I do?