NT 4 Software Raid failure during initia

I am trying to set up a mirror set on 2 physical disks (IDE) using the software raid features on NT4 Server (6a). The OS is on a separate logical drive on one of the disks and is not being mirrored at this time. During the initialization period the server crashes after approx 12 of 15GB has been mirrored (this has been found from spliting the mirror afterwards). I suspect I have a HW fault but nothing appears obvious. The server is not being accessed by users during this. Does anyone have any ideas ?