How do I get the Dashboard to show up on the Launchpad key?

So I have an iMac running Snow Leopard and a MacBook Air running Lion.

I use the Dashboard quite often and I really want to be able to access it using the Dashboard key on Snow Leopard computers.

Currently I'm using fn+F4 to do it, but I'd much rather just click the Launchpad key.

Since Lion came out, Macs that came running Lion had the Dashboard key replaced with the Laucnhpad key. And my brother upgraded his MBP to Lion, obviously the key was a Dashboard key, but it didn't change to Launchpad, it's still Dashboard.

So my question is, can I change the function of the Launchpad key to be the Dashboard key? I'm finding it OK just hitting fn+F4, but I'd rather just be able to hit F4 (as in, the Launchpad key)

Edit: Also, plugging in the keyboard from my iMac, if I hit the Dashboard key, up comes the Dashboard. Is it something to do with the hardware?