I don't know how to open the battery door for the

Question edited to add full make and model.
Question moved from Dishwashers to Canon PowerShot A630.

https://www.google.com/search?q=take+the+back+off+the+screen+of+A630+camera

Personally, I would send it to Canon for professional service. It may just be a problem with insufficient battery milliamps.

https://www.google.com/search?q=A630+camera+E24+Error+Code

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Things to check first for a camera that won't turn on are battery contact points, and micro switches that are located on the battery and memory card doors. Troubleshooting tips on other things that need to be checked may be seen here. These tips won't work for every case, but they're worth a try.

Take a blade screwdriver and rub the end of it on the contact surfaces of the battery termanels In the lower end of the battery hole use a flashlight if needed. then visualy place the batteries in the battery holes making sure they extend high enough to create contact with the cover if not gently pry up the lower terminals to create this effect. now make sure the upper battery contacts are clean by rubbing them with the screw driver end then make sure they extend above the plactic in them if not bend them so as to have a good spring pressure on the batteries. then try turning on camera, the high amps needed to turn the camera on will cause a minute arc that then is a open cicuit and not allow camera to turn on, also the open and closing of battery door for the sd card will cause tension to be lost in the contacts. don't be afraid if you have to really push the door down to close. Hope this works for you.

Open your battery door. See this picture. Notice the little door saying CR1220? Pry it open with your fingernail. The enclosed CR1220 battery is the camera's "watch" battery for time and date. Sounds like it may be "time" for a replacement. Take the battery to your local drugstore to purchase a replacement. Don't know why, but drugstores seem to have this battery at a more reasonable price (~$3) than W-Mart or other retail store (~$7).

Here's some tips on fixing stuck automatic lens covers. Good luck!

Try NOT connecting your camera to your computer.

The best way to download pictures from your camera to your computer involves removing the memory card from the camera and plugging it into a card reader (either built-in to the computer or connected via USB or FireWire). This is likely to be faster than connecting the camera to the computer, and won't run down your camera's batteries.

Once the card is plugged in, it will appear to your computer as a removable drive. You can use the operating system's drag&drop facility to copy pictures from the card to the computer's hard drive, the same way you copy any other files. Or you can use Canon ZoomBrowser or any other photo cataloging program.

Ebay, Canon, Amazon.com, Tigerdirect.com

This is an old A70, but the way it's done is very similar as I don't think this has changed much over the years. It's a pin design that you have to push out with a stiff unbent paperclip. You push in on the side with the smaller hole. To access the pin you'll need to remove the front and back case covers. See the following:

http://blog.thustra.com/2007/03/canon-a70-ir-modification.html

"It shouldn't do that." But you already know that. Even with everything "on" in the camera it still shouldn't do that.

I think you need to try a) alkaline batteries and b) new NiMh batteries. If it still persists then your camera has a deeper problem and needs to be sent in for repair.