Then yes, you would run Server 2003 as an Active Directory Domain Controller (beware: the setup for this kind of thing is very very involved).
And to be able to do all the usual multimedia tasks on it, you have to manually enable DirectX, manually enable sound, etc, but its doable.
For instance, my TV card is in my Server 2003 box because there aren't any 64 bit drivers for it yet, and it works just fine on there.
Desktop machine: 2 x Opteron 246, Asus K8N-DL, 2GB PC3200 ECC Reg., XFX GeForce 6600GT, 74gb WD Raptor, 2 x 19\" LCDs, Windows XP x64
Server machine: Intel P4 3.0GHz 2MB EM64T, ECS i865pe, 1GB PC3200, 36gb WD Raptor, Windows Server 2003
Laptop: Dell Inspiron 9100 (Intel P4 3.2GHz 1MB Prescott, i865pe, 512MB PC3200, Mobility Radeon 9700, DVD+R/DL Burner), Windows XP
Linux: P3 450Mhz, 386MB ram, Slackware 10.1 (Running mySQL/Apache)