Do all computers output digital thru USB?


Forgive my newbee question but I want to output a digital signal to my USB DAC from my computer. How do I know if my computer outputs digital thru its USB port or analog? How do I get a digital stream to output to my DAC? Thanks for the look and the help. Really.
128x128pugstub
Go to
Control panel>>Sounds and Audio Device Properties
Click Audio Tab
Change Sound Playback default device to USB speakers

and then click apply.
Just tried it and still can't figure it out. I am using Windows Vista not XP so it seems to be different. can anyone with familiarity with Vista help? Thanks