Not much you can do with two disks, you can either create a RAID1 mirror and then partition the resulting 500GB logical drive in Windows, or create a RAID0 striped array and partition that in Windows (Not advisable in my opinion).
If this is data you care about I would opt for the RAID1 mirror, or invest in two more disks and create a RAID10 array. According to the docs I see, all the RAID controllers that are supported in this C220 support RAID10, to be sure have a look in CIMC or at BIOS when it's booting to see what model of controller is in it.
