For half a year I've had my HDDs in a striped RAID (RAID 0). A few months ago I saw the first error appear in the taskbar. nVidia MediaShield reported a hardware failure on one of the disks. The errors appeared more and more frequently since then, and the computer halted for some seconds whenever it happened. CHKDSK couldn't do anything about it, as it also halted.
Finally it happened: Windows could no longer boot, so I disabled nVRAID and reinstalled Vista.
The drives of course didn't have any errors. :-(
Update 2007-08-15: As I've now put a lot of files on the non-boot disk, it has actually turned out not to be healty. After some time the computer halts for some seconds and Vista disables the drive. It's time to replace the disk.