One of my servers was giving problems. It was reporting hard drive errors, in various drives, and it wasn't consistent about it. This came to a head when the system drive failed.
So I replaced the system drive, but then I couldn't load Linux on the new drive. Strange!
I thought about this for a while, and decided to replace the motherboard. The old mobo was a P4VP-800, and I've had a few of those, and they do fail. The new mobo worked fine with all the drives.
So I replaced the motherboard, and that seems to have fixed the problem.
But now another server is giving problems, and it's the system drive; when trying to boot, it fails. Fortunately, this isn't a customer-facing drive, so I'll sort it out after Christmas.