One other tip - you might want to check out the Windows Easy Transfer wizard, which is built into your new Windows 7 machine in Start > All Programs > Accessories > System Tools > Windows Easy Transfer. It's not perfect, but it does a pretty good job of gathering up useful files and settings from your old machine and bringing them over to your new one.

Of course, you can also use the computer switch as an opportunity to start over without years of accumulated crud, and if so you may prefer to manually move over files that are important to you rather than letting the wizard attempt to do it automatically. And either way, definitely take a full backup of your old machine before recycling/returning it as insurance against any files that may have been forgotten in the move!