Pictures are over exposed and there are lines all over the pictures

The pictures are over-exposed. if shooting manual, use a smaller aperture and/or a higher shutter speed. If in one of the automatic modes, then reduce ISO value to 100 or 200. Also check your white balance setting.

Kate,
It's six years old - at $90, that represents a mere $15 per annum. Just replace it.

There are two common faults for this problem. 1 is shutter failure and the other is sensor failure. To determine which is simple. For shutter failure put the camera in full optical zoom. Turn off the flash and look through the lens and take a picture. You should see the shutter completely cover the lens inside. Any gaps will result in over exposed pictures or horizontal lines. the other is video mode. if the problem is apparent in video mode too then sensor failure is the likely problem.

if just only raster then can not get any channel the tuner get bad which some parts get burned. if you don't have an idea how to replaced the parts just leave it to the trained tv technician or service shop.tuner is not too expensive unlike replacing an lcd monitor.

it means there is some dead pixel in the screen. you can change one lcd screen and buy then fix it by yourself.
here is the links for the lcd screen,maybe it can help you!
http://skiliwah.en.alibaba.com/product/475587936-210827720/LCD_Display_Screen_for_Canon_Powershot_A470_Digital_Camera.html

It may be that you have inadvertently set your camera to shoot 'bracketing up' - ie over exposing for every shot. You need to look at the exposure ruler which looks something like this: l---l---l---l---l The centre bar is the correct exposure. But there is a little block that sits where you have got your +/- setting at. +/- is the sign for BRACKETING - where you tell the camera to over expose (+) or under expose (-). With Canon if the little block is to the right of the centre bar then you are telling the camera to over expose. Where is your little block? If it is to the right of the centre press your +/- button and turn the dial to the centre bar. NOTE: As digital cameras are WEAK in capturing highlights it is often better to shoot slightly under exposed - with your block set on the first or second horizontal line to the left of the centre bar. This means you are shooting 1/3 or 2/3 of an f/stop under exposed. Hope this helps.

keep iso 100 and set ur screen brightness

Sounds like ccd issue. Some people have reported similar problems when cam is exposed to water (moisture) or if it's been dropped. Contact you local Casio service and ask them details. They probably just say that send the cam to repair but that is expensive, at least in here Europe.

If you are getting fine horizontal lines thet means the picture is over exposing. most probably the apparture or the shutter blade mechanism is not working fine. needs repairs.

This is a failing processor. Check out repair costs from Nikon A new camera may be the better bet.