I had a Inspiron 6400 for quite a while. In fact from models with Core Duo to Core 2 Duo. I had Windows XP and Windows Vista installed and run from these laptop. I ever had Ubuntu in it for a while.
Recently, I had just tried Windows 7 on it. To my surprise, there is no need to install any additional driver at all. Everything is regconized and installed properly using the default Windows 7 Build 7000 Beta. The only thing that needed update was the Nvidia 7300 Go driver which was installed directly from Microsoft Update.
Nvidia has changed its model from downloading individual drivers to gettign it integrated into Windows Update for Windows 7. For now, anyway.
Dell Inspiron has spanned 3 generations of OS - Windows XP, Windows Vista to Windows 7. I had even the 64 bits edition running on the Core 2 Duo models. I do not think you will find another laptop which could be as compatible. I had a Compaq laptop which doesn't even comes with Winows XP drivers!