Regarding IBM eserver adding new hard drives to raid

Hi,
I have IBM eserver x series which has two U320 73.4GB SCSI Hard Drives 32P0727, and it hardware raid enabled for mirror, its installed with windows 2003 server, as i am running out of low disk space in C drive i required to add up more space in C drive, this server is the main server in our organization, and i doesnt want to take a risk of doign anything, so can you suggest me if i get 2 new same configuration harddisk and add in hardware raid will it add one hard drive for c and other for mirror is it possible if not possible then suggest me how can i do this…. its very urgent guys..

Thanks in advance