Dell Optiplex GX620 systems and Windows Vista
Good news: Windows Vista natively supports all components in the typical Dell Optiplex GX620.
Bad news: except for audio.
Worse: Dell lists no Vista drivers of any sort as of this writing on their support site for the GX620.
Dell USA does not list any audio drivers on their support page or training pages, and a call to Dell Gold Support turned up nothing at this time. Cyril at Dell Gold had me try the Optiplex 755 driver, but that returned an error. However a google search turns this up:
R145149.exe is the packaged Dell ADI 64 Bit Onboard Sound Driver for Vista x64 for the following systems:
Dell Precision WorkStation 370
Dell Precision WorkStation 470
Dell Precision WorkStation 670
This has been installed successfully on Windows Vista Enterprise x64 and passed on to Dell for inclusion in their records.