Hi! I have a problem which I hope someone here can solve!

I am currently writing my University dissertation in Word 2007, and as usual for my department I have to double-space my work. I know how to do this in Word but currently when I highlight a paragraph to double space and apply the change in the paragraph option, it applies the new paragraph spacing to every part of the document and not just the part of the text I highlighted.

I have asked numerous people to help fix this problem but they can't seem to find any solution whatsoever, and I have no idea why this is even happening anyway!

If anyone has any ideas to help fix this it would be really appreciated! Thanks!