Reinstalling Windows 7 without a Disc

The information was taken from a pcworld article, "How to install windows 7 without the disc".

1. Find your Windows 7 product key: Typically this 25-character alphanumeric string is printed on a sticker affixed to your PC or on documentation included with your PC. 

2. Download the ISO file for the version of Windows 7 you own:

• Home Premium SP1 (English, 64-bit)
• Professional SP1 (English, 64-bit)
• Ultimate SP1 (English, 64-bit)
• Home Premium SP1 (English, 32-bit)
• Professional SP1 (English, 32-bit)
• Ultimate SP1 (English, 32-bit)

The above links point to Digital River, a licensed distributor of Microsoft software. These downloads are each over 3GB, and your product key will work only with your edition of Windows, so make sure to select the right one.

3. With the ISO image burn it to disc and boot. Check the blog, "Burn iso image file to a dvd".