Each time I started my PC, one of the boot-up screens was showing an error (edited):
Intel matrix storage manager Rom v5.1.2.1002 ICH7R wRAID5
Hitachi HDP72505 S/N: GEA530RE3YJRBA 465.8GB
Drive 0: Normal
Drive 1: Error Occurred(0)
Hitachi HDP72505 S/N: GEA530RE3YJRBA 465.8GB
Drive 0: Normal
Drive 1: Error Occurred(0)
Since my PC was still working, and I my hard disk was showing more than 465.8GB full, then the second physical drive must be working OK, despite the error message.