Here's a bonus tip.
Unlike Windows Vista, Windows 7 removed the ability to choose which edition you want to install, due to confusion by the average consumer I'm sure. But, this is easy to fix, especially since you'll be installing the OS from a thumb drive. After your drive is completely prepared and you verify that it boots fine, boot into an OS and open up the 'ei.cfg' file under the Sources folder.
Because Windows doesn't open this by default, you can choose to open it with Notepad, or right-click the file and use the "Open With" option. Once its open, the layout will be like this:
[EditionID]
Ultimate
[Channel]
Retail
[VL]
0
Notice the "Ultimate"? That means it will default to that version of the OS during the installation. You can either change this to another version, or delete the entire file, which will cause you to see the version choice during the installer. See? Now that's an easy problem to fix!
The proper version names are:
Ultimate
Professional
HomePremium
HomeBasic
Starter