I can't connect my Dell Studio 15 to my Sony TV - (Newbie)?

Hi there,

This is my first post so I apologise if i am in the wrong place etc. etc.

My problem is I use to connect my Dell Studio 1555 to my Sony TV on a regular basis but since I connected the laptop to a Samsung TV I no longer get a picture when I connect it back to the Sony.

It works perfectly fine on the Samsung still but unfortunately that TV isn't mine.

It's driving me nuts so hopefully somebody can help me, please