A short one: those of you who may have installed Windows Server 2008 (beginning with RC0 through the RTM) have discovered that no audio driver is available, for the VM's simulated device.
This was doubly annoying, since the OS resorts to using the onboard speaker (loud beeps, no way to control the volume).
Aaron Tiensivu found the right driver, hidden somewhere in the Microsoft Update site, but no longer offered as an automatic download. And it works! (Apparently it also solves Vista issues, although I never ran into those).
Download the driver here and if it's ever taken down, I've saved a copy here.