Digital cameras: hp photosmart r937 problem- horazontal lines help!!!!!!

hp photosmart r937 problem- horazontal lines help!!!!!!

i have this digital camera with a tuochscreen and a bunch of settings that im not super familiar with and iv been using it for years but all of a sudden after a while of non use it has been putting light and dark horazontal lines in some or most of my pictures. the 3 second preview after i take the picture is perfect and then when i go back to look at it on the camera or on the computer it has horazontal lines throughout the picture. i have a 2gig sd card in it which also replicates the problem. I have tried taking it out and seeing if something is corrupted on the card and the internal memory does the same thing. video recording on the camera however does not do this. the flash setting does not make a difference as well as any of the other settings i altered and tried on or off. could there be something wrong with its method to store pictures or what? please tell me anything that might give me a hint, i paid 300 dollars for this camera and cannot afford a new one and my best friends wedding is very soon