I accidentally dropped my samsung S1070 while I was taking a photo, and the lens is now stuck out. It won't turn on, and we've tried replacing the batteries and taking them out. I've also tried...
Check whether your batteries are actually making contact with the battery posts, and that these posts are clean. If not, bend the posts up/down a little, and maybe clean them with a little rubbing alcohol on a Q-tip.The next thing to try is examine both the battery and flash card door. There's usually a little switch on both doors (note some SD card doors do not have this switch) that activates when the doors are closed. If they don't, the camera won't start to prevent damage to the flash card or camera startup sequence. For most cameras its usually a little piece of plastic on the door that pushes in on a pin switch when the door is closed. Closely examine both doors to try to identify these switches. A lot of times that little plastic nib wears down or breaks off, but can easily be jury rigged with a small glued-on replacement.
If you've tried all of the above and still no luck, the problem is then likely to be internal to the camera. One example would be that if your camera uses Compact Flash, check to make sure all pins are present and aligned in the card slot (if bent, simply unbend/straighten them with a skinny "jewelers" screwdriver, then insert the flash card for final realignment).