If you have problems with the DVD install try this:
You can download the USB tool for free and copy your Windows 7 ISO to the USB. Complete instructions can be found here: http://store.microsoft.com/Help/ISO-Tool
I use USB flash drives all the time for OS install it works perfectly - lot faster and no DVDs to get scratched and damaged! :-)
Step 1. Close all applications and program windows that are currently open by clicking on the "X" symbol in the upper-right corner.
Step 2. Open the Start menu by clicking on the icon in the lower-left corner of the screen.
Step 3. Click on the "Shut Down" button. A pop-up window will open with several shutdown options.
Step 4. Select "Restart" from the list of options, and then click the "OK" button. The computer will shut down, and once it is fully turned off, the system will reboot and load the Windows operating system.