1) Wander over here: http://www.via.com.tw/en/products/peripherals/serial-ata_raid/vt6421/
and download the latest drivers for your OS and read the directions.
2) If it still freezes with the latest drivers and a newly-built RAID array, return it if it is in warranty and throw it out if it is not.
That is one old device. It's top speed will be limited by the SATA I interfaces and the old PCI 33 MHZ bus.