why doesn't my Ipad show up on my PC as a storage device

Because it isn't a storage device.

Allan

It's not designed to. It will only appear in Windows Explorer if you have photos on the iPad that were taken with it, copied to it via the camera connection kit, or saved from emails, websites - in which case it will appear as a camera. Otherwise you get content on and off the iPad via the file sharing section at the bottom of the device's apps tab when connected to your computer's iTunes, via wifi, email, dropbox etc