Any ideas what would cause the SATA Mode setting in the BIOS to get changed from its default value of AHCI to IDE? The change causes Win7 to be unable to boot until it's changed back to AHCI. As far as I can tell nobody is going into the BIOS and changing anything. The machine is only about a year old, so I don't think the CMOS battery is failing. Even if it was the default setting is AHCI anyway.
The motherboard is a Gigabyte GA-B85-HD3.
The motherboard is a Gigabyte GA-B85-HD3.