Boot with the Windows 7 DVD.
You'll get the options of upgrading or to do a clean install.
If you chose to upgrade, all installed applications and drivers will be preserved as well as your settings and files.
Next, get the drivers bundle for Windows 7 from the Dell web site. Run the driver's installer and that's all.
If you chose the clean install, you'll be asked what partition or drive to use and get the possibility of formating it.
You'll get a warning that any information contained on that partition will be lost. Just go ahead and launch the formating process.
In this case, any file on the main partition will whipped clean, all settings will be set to default and there will be no applications installed unless there are some bundeled ones. You'll start with the default, Microsoft supplied, drivers. It's recomended to get more specific drivers. You should be able to get a drivers bundle from the Dell web site, under support.
Electro
June 2013