See my Windows Reinstallation Guide/A Clean Install of Windows 7:
Use a Digital River .iso and the Activation Backup and Recovery Program:
You can download the version of Windows 7 that matches your license here: http://www.w7forums.com/threads/official-windows-7-sp1-iso-image-downloads.12325/
Then activate using the product key on the COA/sticker on you computer (usually requires phone activation).
After installation, you can get the drivers you need by finding your model here:
Start with System Software (if applicable), then chipset drivers, followed by any others that are available on the Support Site that matches your specific hardware (video, wireless, audio can vary by configuration ordered).