Instructions
Open your web browser and visit the Battle.net "Download Games" site.
Click the "Windows" button next to the term "Full Game Client" in the "World of Warcraft" portion of the window on screen. Select "Save As" to save the downloaded file to your hard drive.
Insert a flash drive into your computer.
Click "Start" and choose "Computer." Open your flash drive icon. Click on the Blizzard "World of Warcraft" file you downloaded and drag it into the flash drive folder. This copies the file to the drive.
Remove the flash drive from your computer and put it into a USB port on the Windows 7 computer you're trying to copy the files to.
Click "Start" and "Computer." Open the flash drive icon and double-click the "World of Warcraft" file. Provide your Battle.net user name and password. The client will download and install "World of Warcraft" as well as the most recently available patches to the Windows 7 computer.