how can I allocate hard drives?

I just installed Small business server 2011 essentials and I had configured all 4 2 tb hard drives as RAID 0, not realizing that SBS won’t see any partition or HD over 2 tb. I can reduce the size of the 2 TB partition and I can see the 5402 GB in the disk manager but it will not allow me to do anything with it. Is there another way to allocate it? I tried diskpart from the cmd but it did not show up.