Ummm replace the CMOS Battery?

I have a canon powershot a620 it will not actually turn on. when the power button is depressed, the power light comes on, the lens extends, the screen stays black, and within a minute the power light goes off, the lens stays out and you can push the power button all day and nothing. Move the switch to view pictures press the power button, the lens retracts and the view screen lights up with the blue canon logo, within a minute the screen goes black, nada, zip, nothing. So in the trouble shooting guide i saw what looked to be the closest with no power. The CMOS Battery. I followed the step by step (very good) instructions. Which brings me to my question. Where is the CMOS Battery? I figured i would see a button battery and would figure it out pretty quick. ;P Which brings me to a second question if i may. Am I barking up the correct tree? Thank you for your patients with my babbling.

Max