Do you have a manual? I don't have mine anymore or I would look it up but look at the section on flash and you should find instructions on how to set it up. I rarely used Auto or Program modes so I don't remember exactly how it works but if you use those modes you are allowing the camera to make all the exposure decisions and apparently it is sensing low light levels requiring flash. You need to move to Av, TV, or M modes to gain more control of the flash. I don't remember how the fill flash is set up but it may be that you have that function turned on. I wish I could be more help but it has been a long time since I used the onboard flash on my camera. If you don't have a manual you can download a copy. The manual is your friend so keep it close by as you are learning to use your camera.
Normally if you raise the pop-up flash it tells the camera that you actually WANT to use it (so it will) are you raising the flash or is it popping up on it's own?
