If you are using Windows software RAID, you could monitor the event log to see if a disk fails. Unfortunately, I don't know what messages might be relevant.
If you are using hardware RAID from HP or Dell (probably others as well), you can use the vendor-supplied agents to monitor the system via SNMP using devmon.
/Johan
From: Larry Barber [mailto:user-6ef9c2864140@xymon.invalid]
Sent: den 2 november 2010 16:09
To: xymon at xymon.com
Subject: [xymon] Disk failures
Can Hobbit detect when a RAID disk fails on a Windows box? If so, how does it show up?
Thanks,
Larry Barber