How do I turn my flash off?

Sure: Solution #1. Stop dropping it.;) Solution #2. Send it in for service. Be prepared...it will be expensive.

Hi,

If this is the case, the camera might have internal damage. Might be better to send it back to Canon delears/shop for repair. Please try below link

Canon

Press the flash button (right on the multiselector, marked with a lightning bolt) repeatedly to cycle through the various flash modes. To turn off the flash, select the lightning bolt in a circle with a slash through it. Don't forget to turn it back on later if you want it to flash.

The problem could be that the room is too big. Try taking pictures closer to the wall, so the flash can bounce back more effectivly.

It sounds like your flash unit is broken. If you can DIY, try to open the camera, check the fuse and the inductor on the flash unit. Here is a tip for your reference:
How to fix a Canon SD750 with intermittent flash problem

Just remove the screws, than SLOWLY pull apart.

Hi

Your flash is defective, or the mainboard is defective and cannot control the flash. The only way to figure out which is the problem is to start by replacing the flash and see if it works.

You can probably find a parts camera online and use it to fix yours, if not let us know and we can help. We are an affordable digital camera repair business.

Thomas
Owner- Darntoothysam com

There is a cold solder on the flash unit. If you want to DIY, here is a tips for your reference
How to fix a Canon SD750 with intermittent flash problem

The manual says the flash range is 1' to 1.6 feet with setting the ISO speed to auto.

This setting will be in the MENU settings:

• AiAF: Sets AiAF to On, Off, or activates Face Detection.
• Digital Zoom: Can be set to Off, 1.5x, 1.9x, or Standard.
• Slow Synchro: Allows you to shoot with the flash at slow shutter speeds, useful at night.
• http://www.imaging-resource.com/PRODS/SD750/SD750A3.HTM