If the user has the standard Integrated Audio, it requires a Dell driver to work or work correctly. We have found that non-Dell sound drivers, in most cases of these "older" models, does not work. With SigmaTel, Windows will usually install IDT drivers and the newer IDT drivers do not work with the older Dell SigmaTel implementation.
As there are Dell Vista 32 bit drivers it should work OK with Win 7 32 bit. However, with many older Dell's that do not have Vista drivers users are having to install PCI sound cards to get sound in Win 7.