How to rearrange/remap/change the keys on your keyboard

I recently needed to rearrange my keyboard, and when I google'd it, the information was surprisingly sparse, so I thought I'd add how I do it to the mix.
A few days ago, I accidently knocked the Enter Key off my keyboard (Don't ask me how), and it was seemingly impossible to reattach. I therefore decided to simply rearrange the keys on my keyboard, so that another key could be the Enter key.
Here's a simple guide I wrote up for it:

1. Download and install KeyTweak. (the file called KeyTweak_install.exe). It's compatible with all +2000 versions of Windows (Windows XP, Windows Vista and Windows 7), and it should be compatible with Mac OS X too.
2. Open up the program and click any key that you want to change, then choose what function you want it to have from a simple list containing all the keyboard shortcuts imaginable, then click 'Remap Key'.
3. When you're done rearranging your keyboard,  click 'Apply'.
4. You should now be prompted to restart your computer. Do that.
5. When the computer has restarted, your keys should be rearranged. You might notice a slower start-up, but that's because your computer has to update its registry.

Here's a screenshot of the interface of the program: