I have a windows 2003 server with a Software RAID either 1, 0+1, or 5. (Not sure didn't set it up and haven't looked at it yet.) The OS Disc is the one that has failed. What are my recovery options here? for any of these will replacing the failed disc help me or would the OS Disc have most of the recovery data on it?

For the OS, it is likely a RAID 1. One way you can tell if you're using a software RAID is by going to Computer Management -> Disk Management and look at the C: drive. If you see Mirror or if Fault Tolerance is set to Yes, then software RAID is configured. If the OS detected a failed drive, the Disk Management may even indicate which one; eg, SCSI 0 or SCSI 1, etc. If drive C: is in fact mirrored and you know which drive is bad, you can simply remove the failed drive, insert a new one, and within seconds, it will start to sync. Once the sync is complete, will take awhile depending on disk size, you have a complete mirrored OS. BE CAREFUL: be sure you pull the correct(FAILED DRIVE) out. Now, if you don't see Mirror or Fault Tolerance is not set to Yes in Disk Management, that doesn't mean that your disk isn't configured in RAID. It may be configured in hardware RAID. Unfortunately, and depending on your RAID infrastructure, sometimes you can't tell if hardware RAID is configured without rebooting the computer and going into the SCSI configuration utility and browse the volumes. Hope that helps and good luck. jav

Update: This is a Software RAID 5 System. The RAID 5 configuration however was setup after the OS was installed for additional data drives. The system can't boot because of the failed disc. There is no hardware RAID setup. Since the RAID was setup after the OS and not with it does that mean my RAID is useless since C: is the failed drive?

Strange. RAID 1(never tried RAID 5 for OS before) after the OS is installed should be fine. If your system can't boot, and you're certain it's RAID 1 or 5, then either you have two or more drive went bad the same time or corrupted system files preventing your system from booting. Your option at this point is limited only to fresh install/restore, unfortunately.