projection problems

I'm fairly new to this game but I've just started doing Powerpoint slide shows as part of worship in our local church. The first few have run fine, but now suddenly my laptop's (Inspiron 1100) adopted something called 'presentation mode' and is reducing my on screen and projected images to something like 3/4 size. Can anyone solve it. For my laptop to recognise my projector (a Sony VPL-CS6) I have to press Fn F8, though I think that's supposed to happen -according to the projector manual some computers require additional keys to run the hardware. Simple one syllable word replies appreciated - I'm a complete novice with the technical jargon!

This message has been posted once, but someone told me I was in the wrong section - I told you I was a novice!