live backup of server data on diff pc

Config :
NT server running a dos based (clipper) application which is accessed across a workgroup.
Application database is around 900 MB and growing stored on on the server and accessed using drive mapping.
Server is RAID 5 configured
Backupserver running NT
Query : How do enable live data mirroring of server data on the backup server so that in case of primary server failur my backup server takes over ( either manually or automatically )
I would also like to know if there is any non proprietory way of doing this cause I am unable to purchase most of available software solutions to do the same locally in india and i’d prefer to buy something with support included.