First, try downloading it again, and burning to the disc at a slower speed.
Download here Official Windows 7 SP1 ISO from Digital River « My Digital Life
make sure you get the version that your product key is. Then, burn at the slowest speed using ImgBurn.
Also, could you fill in your system specs?
Here's how: System Info - See Your System Specs Under System Manufacturer/Model Number add whether it is a desktop or laptop and whether self built. Log in to Seven Forums and you will be able to transfer the info directly to the specs page in your profile from within the System Info app.
After doing this your specs will be available in each of your posts. Click on mine in the lower left to see how it should look.