Click on the link at the bottom of the page to open Dell download page.
Using the form on the Dell page, choose the OS (XP or Vista), the
download links will be listed on the lower part of the Dell page.
Download one by one the drivers listed on the last part of the Dell
page (audio, video etc.) by clicking the link for each driver.
Save the drivers into a folder, renaming them as audio, video etc. When
you have finished downloading all drivers install them one by one onto
the Inspiron 6400 by executing the files that you just finished
You may need to restart the computer after installing each
driver.Ensure that the driver installation is complete before
Ensure that you are using an account with administrator privileges
while installing the drivers. If using Vista you may need to click the
right button of the mousepad on the installer file, and choose 'Run as
Administrator' from the drop down menu.
Here the download page: Drivers & Downloads
Note: drivers for Windows 7 and Windows 64 OS are not available.