The driver disabled the write cache on device \Device\Harddisk0\DR0.
I got this event a few minutes after I had enabled the write cache in Vista for my RAID 0 array.
It turns out that my Intel Matrix Storage RAID controller is already doing write caching, and as such turned this option back off.
On workstations you can verify this by opening the "Intel (c) Matrix Storage Console" and switching to "Advanced Mode" in the "View" menu.
Click a HD under the "RAID Hard Drives" container (or the Array_000x under "Arrays") and verify the "Hard Drive Write Cache Enabled" setting. If it's set to "Yes", then the driver is already set to perform write caching.