My sister has two Canon cameras and the second one displaced the first one's software. I am beginning to use an A3300IS, but my daughter has a Canon SLR on this computer. She's on vacation, don't know which one, but am hesitant to download the software for the A3300IS unless I know more. Maybe I'll wait two weeks.
You can use the same camera photo library software for both cameras. The camera-specific software is different for PowerShots vs. DSLR cameras. The DSLR will use "EOS Utility" to control the camera. The PowerShot will use a utility named "CameraWindow".
You can mix cameras with the same computer without conflict. If you go to the Canon website at http://www.usa.canon.com/cusa/consumer/products/cameras then find your camera. Pick "Drivers and Software", then select the OS type and version. Canon will display a list of all associated software. Just make sure you update everything to the latest version (unfortunately there's no neat utility to self-update them... which would be nice (hint hint Canon!))
As far as I am aware, Canon's software (at least for Powershots) isn't really camera model specific. For eample, Camera Window (for Mac) when I bought my 280 last month is an upgraded version of Camera Window that came with my 1300is 3 years ago. The older version on my computer will not recognize the 280 but I presume the 280's version would recognize a slightly older camera (I can't run the newer version on my computer). I know once I had the actual photos downloaded to my computer (which I did using a card reader) the older ImageBrowser had no problem with the 280's jpegs though it wouldn't play the .mp4 movies since back then Canon was using motion jpeg and .avi.
It would help if you let people know which specific software you are trying to use.