Weird bootup problem?

Yesterday I almost cried when my PC didn't restart properly. As you know I already had to do a fallback because of service pack 1.

I only rebooted the PC normally, but when it tried to restart, it stopped at a blank screen with the underscore cursor blinking, nothing else. Tried to reboot again, but the same.

Strangely while booting up, I didn't hear any HDD spinning, so I thought that might be an issue. So I entered BIOS, but saw that it was booting correctly from the HDD and not any other device.

Saved and rebooted again, same thing. So I opened the PC and checked my cables, not that one of them came loose, but everything looked just fine.

So I booted again into BIOS and checked my HDDs. I have 5 of them, and they are all the same, hence the name is the same for every HDD, and you don't see which one is which, a little bit annoying, but only when you have to fiddle around with them.

But I noticed that HDD 1 was set as HDD 4, and HDD 5 was set as HDD1, which I thought was a bit strange. I looked then further, and saw that the HDDs have in front of their name 2 letters, different ones. And the HDD which was booting at the moment had PS, and the before mentioned now 4th HDD had PM. So that left me with the strong feeling that PS was standing for slave, and PM for master. So I put the PM HDD as the one to boot from, left BIOS, and look there, it booted again normally.

The only thing that I'm still asking myself is, how the heck could this change without touching anything BIOS wise or even in Windows?? The only thing I did was adding a NAS to my system, as I bought one for my movies and series to use with my new media player. And as the software didn't work correctly, I rebooted.

Have no idea what could have been the problem.

I've seen this before - hard drive boot priorities changing in the bios by themselves. Sometimes caused by plugging in a USB device or another drive which can be bootable. Once you've reset the order after adding a new drive/device and saved, the bios should remember it.

Not sure what causes it otherwise, perhaps some bug with SATA or AHCI and hot swap capability. It is quite rare however, so keep an eye on it. Just seems to spring up now and again.

SATA has caused a few issue with me, I think I've mentioned it in the past. Not as robust as good old IDE and could have been designed much better. The cables can easily go bad, make poor contact, don't like bends and get knocked out of sockets if no latches.

Also I'm finding modern SATA disks have quality control issues - the high density surfaces are of varying quality (more common to see reallocated sectors, many more slow sectors exist today). The same drive models can have different performance characteristics, surface quality, access times and acoustics (varying whining, vibration, seek noise). Had this problem with Samsung, WD and Seagate. Two identical drives having good and bad examples but passing for retail, probably because most people wouldn't notice unless they ran tests. It's becoming luck of the draw!

I plugged an external disk in which wasn't plugged in for a long time, and it was still inside the USB plug when the PC rebooted, maybe that was the problem.

I remember now that exactly this disk made problems with my old PC, when it was plugged in and I rebooted, the PC wouldn't boot at all, until I unplugged the disk. It's a smaller 120GB WD 2.5" external disk.

I think it's a safe bet that's your problem.

Even USB card readers can cause the same issues too.

I agree. I've had similar issues where a USB stick or external drive had suddenly rearranged my drive order.

I have in the past also had the strange issue where the system wouldn't boot and looking in the BIOS the drives were in the wrong order and the boot drive was not set as the first to boot from.

Something else to do just to make sure is change the BIOS coin battery. A failing battery can cause these issues too, although as you have realised the cause could be the eternal HDD it probably isn't that.