Accept the license terms and choose the Custom (advanced) installation type.
If Windows 7 is still running and you only want to erase an extra hard drive (not the drive where Windows lives):
For those needing more control, the Disk Management snap-in ( diskmgmt.msc ) is the standard tool. format windows 7 hard drive
Press the key required to enter the Boot Menu (usually F12, F11, or Esc). Select the DVD or USB drive as the boot device. When prompted, press any key to boot from the media. Select your language and keyboard layout, then click Next. Click Install Now.
Formatting a Windows 7 hard drive is easy once you understand the rules. Drives D/E: can be done inside Windows. Accept the license terms and choose the Custom
Option 3: Format the Primary C: Drive (Reinstalling Windows)
The Command Prompt offers a more direct way to clear a drive, which is useful if the graphical interface is unresponsive. Open the Start menu and type cmd. Select the DVD or USB drive as the boot device
Once the format is complete, you can continue the installation or exit if you only intended to wipe the drive. Understanding Quick vs. Full Format
When you format a drive, you will often see a "Quick Format" checkbox.
Full Format: This scans the drive for bad sectors and completely overwrites the data. It takes much longer but is safer if you are selling the drive or suspect it is failing. If you'd like to get more specific, let me know: