My computer turns itself off everytime something is plugged into the USB. This only occured after uploading some photos from a digital camera.

That does not sound good. How are you removing the camera? This could be a cache problem. To minimize cache related problems, under My Computer, right click on the Removable Device, then select Properties > Hardware, then highlight the removable device and select Properties > Policies, then ensure the "Optimize for quick removal" radio button is ticked and then "Ok" your way back out. You still should wait a second or two to ensure any required "housekeeping" is complete, but then you can safely remove/disconnect the USB device without going through the Safely Remove Hardware icon.

I dont have a problem with taking things out but i just cant get them in in the first place to change the devices properties.

How many USB devices are plugged in? Note that if the devices are drawing power from the USB port , too many devices may be attempting to draw too much power, causing the PSU to choke. You might consider using a self-powered USB hub.

It has 6 usb ports and all 6 have been used before at once without problems. The digital camera isnt recognised on any computer any more even a new laptop. Could a fault with the camera caused a problem with the computer?

Could a fault with the camera caused a problem with the computer?

Sure. A fault with any peripheral device can cause a problem if connect to a computer, depending on the specific fault. Could be the cable too.

So if it was the camera that has affected the USB then how do i fix the USB for the other devices to work.

So now nothing works in any USB ports? Or just one pair of USB ports? Are there any errors in device manager?

The 2 usb at the back used for mouse and keyboard work. 4 usb at front dont work with anything ipod etc.

Then the one in front, which uses a different controller, sounds like it fried. It happens. Again, look in device manager for errors. You may just end up needing a hub you connect to the back, that you can place in a more convenient location, and connect your front loading devices to it.