Has this laptop ever recognized your camera as a device? If yes, then unplug the camera from the laptop, reboot, wait until your laptop quits loading everything at startup and then plug the camera in to your laptop. Sometimes when your laptop resumes (from having gone to sleep or hibernating) it doesn't probe all connected devices, so it knows something is connected to the USB port but it doesn't remember what, and it doesn't try to find out either. Reinserting a device in a USB port may not trigger your computer to recheck the device either, resulting in an unrecognized device. If you switch USB ports, you can sometimes end up with a situation where the computer realizes that the same device is being connected to a different port, but it doesn't remember what the device is, so it goes unrecognized again.
Originally posted by elliott Is the camera in MSC or PTP mode for USB?
PTP mode is useful if you have a program that starts automatically to download pictures from your camera once it is connected to the computer. However, it only works if your computer has a driver registered to use with the camera. MSC is Mass Storage Class, and in that mode, your computer treats your camera like a memory stick or card reader. You have to transfer files manually, which may or may not be inconvenient for you.
If this laptop has never recognized your camera (so it has never prompted you to download or transfer pictures to your laptop), and you wish to use PTP mode, unplug the camera from your laptop and check the setting on the camera. If it is set to PTP, turn off the camera and reboot your laptop. Just as above, wait until it quits loading everything for startup, insert the USB cable from your camera and then turn the camera on. Your laptop should indicate that a device has been connected to it (usually by making a sound), and it should start probing that device and try to locate a driver for your camera. Worse case scenario, your laptop will ask if you want to search the Internet for a driver, but usually a generic PTP driver is good enough and the whole process shouldn't take more than 30 seconds, assuming there isn't another program running in the background (to update iTunes or your browser, for instance). Depending on what AutoPlay options are set for your laptop, you may not get a prompt to download pictures, but if you go to My Computer, you should see your camera listed as some kind of device (usually removable storage).