Insert the Windows 7 installation DVD, and then start the installation.
Select your preferences in the Language to install, Time and currency format and Keyboard or input method options. Then click Next.
Click Install now.
In the screen of the Microsoft license agreement, click I accept the terms of license, and then click Next.
Click Custom (Advanced).
Select Disk 0 partition 1, and click Delete.
Click OK when propmted.
Select Disk 0 partition 2, and click Delete.
Click OK when propmted.
Click New.
Define the size of the disk, and then click Apply.
Click OK when propmted.
Select Disk 0 partition 2, and then click Formatting.
Click OK when propmted.
Formatting should complete correctly. Click Next to continue.