SD870IS Download Problems

I've owned an SD870IS for several months & have had picture download problems from day one. Currently the computer doesn't even recognize that the camera is attached. I can't download anything. When attaching my previous Sony camera to the USB a window would automatically appear asking me what I'd like to do. From there I'd view files & cut & paste. It would be so much more convenient if I was able to use my Cannon in the same way. Is anyone familiar with how I might be able to explore the files on the camera? Am I missing a driver? I'm at a loss here.........

Try using a card reader as a drive.

I've noticed on my computer (xp) that every so often the computer fails to recognize camera.....tried moving cable to different usb port and it seems to work. I've moved it back later and it worked on the old usb port, it is kind of flaky. I think powering down the computer before the cable is attached to the camera, helps.