Here is how to make clean install of Windows 7:
1. Boot the computer from your Windows 7 installation DVD.
NOTE: Make sure that the CD/DVD drive is selected first in the boot order in your BIOS settings. Usually it is by default.
2. When prompted, press any key to boot from the installation DVD.
NOTE: You will only have about 8 seconds to press this key. If you miss it, you will have to restart the computer.
3. Set up your language preferences and click on the Next button.
4. Click on the Install Now button to start the installation.
5. Check the I accept the license terms box and click on Next.
6. Click on the Custom (advanced) option.
7. Select the hard drive or partition that you want to install Windows 7 on and click on the Drive Options (advanced) link.
NOTE: If the hard drive or partition that you have selected is unallocated, then you can just click on the Next button instead and go to step 9 since it is blank.
WARNING: You may not have the Drive options (advanced) unless the installation is done at boot, and not running the installation from within your current OS.
8. Select a hard drive or partition that you want to do a clean install of Windows 7 on, then click on the Format option to format it and click on the Next button.
NOTE: If you have a RAID setup, then connect your USB key with the RAID drivers on it, click on Load Driver, select the folder on the USB key that contains the RAID drivers to install them. Afterwards, your RAID drives will be available to select from to install Windows 7 on.
9. The installation of Windows 7 will now begin.
NOTE: During the installation process, your screen may flash and computer will restart a few times.
10. After the final restart, you will see an special screen for a moment.
11. Type in any user name that you want for your default administrator account and any computer name, then click on the Next button.
12. Type in a password you want for your default administrator account. Type it in again to confirm it, then type in a hint for your password. Click on the Next button.
WARNING: The password will be case sensitive. The hint will be seen by all users on the computer, so do not type your password as the hint.
NOTE: If you do not want your user account password protected at this time or do not want to have to type in a hint, then leave this blank and click on the Next button. You can create a password later for your user account in the Control Panel - User Accounts after installing Windows 7 without having to type in a hint.
13. Type in your Windows 7 product key number.
14. Uncheck the Automatically activate Windows when I'm online box, then click on the Next button.
NOTE: You can activate Windows 7 later after you make sure it is running properly.
If you chose to automatically activate Windows 7 online when you set up your computer, automatic activation begins trying to activate your copy of Windows three days after you log on for the first time.
15. Click on Use recommended settings.
16. Select your time zone and set your time and date settings, then click on the Next button.
17. Click on your computer's location to select it for the correct network location type settings to be applied for that location.
NOTE: It is best to select Public location for the best security.
18. Windows 7 will now prepare your desktop to startup.
19. Install all of your device drivers, then Windows Updates.
20. Refresh your Windows Experience Index (WEI) score.
21. When done, all you will need to do is to activate Windows 7.
That's it!