Sidebar disappeared on old pages

Hi, My sidebar has disappeared on all the pages that already existed before I installed this theme on www.penguin-transcription.co.uk The sidebar is on the Home page because I just created a new homepage to make the sidebar come back. It's on the contact us page because that is a page I just created, but it is not on any of the other pages. Please can you let me know a way of fixing this that doesn't involve just getting rid of all my old pages and putting new ones in?! (I hope so!) Thanks,     Anne