The following article explains how to set up RAID 1 (data mirroring) using Windows Server 2003. This requires a dedicated Windows server without a hardware RAID controller and with two hard drives.
Please be advised that setting up software RAID will likely result in a necessary server reboot so please plan accordingly.
First you must log in to your Windows server via Remote Desktop. For more help, please reference How do I log in to my Windows server via Remote Desktop?
You can continue working while the data is synchronized across both disks. Once the synchronization is finished, your system will now be utilizing RAID 1 (data mirroring)!