window server 2003 r2

Hello All,

I am a new user of window srvr r2 and i found out that my c: is only 12 gig and os installed in it. when i check i only have 6 g left, but i have a (4)500 gb raid in the server.
My question is can i add more to this? and how? without doing any damge to my already half way setup, with DNS, Active directory and user, computers. already in place. Please help if you can.

Thank you,

Myrone