A friend called me in panic. A brand-new computer, freshly reinstalled with Windows 7, suddenly wouldn’t boot.

I couldn’t figure it out. I looked up the manufacturer’s 800 number and suggested she call. Sure, I could fix the problem eventually, but the manufacturer would know the quirks of the motherboard they used better than I would. I’ve given up on trying to give anything but the most basic, superficial support of anything I don’t own myself–especially when it’s not sitting in front of me.

He had her change the boot order. For some reason the system was trying to boot off its RAID array before the SSD. That explained why the system took a couple of minutes to get through POST, then spend a few seconds booting. But that didn’t fix the problem.

Finally he asked, “Do you have any external drives plugged into any of the USB ports?”

As it turned out, she did. She unplugged it, and the system booted right up.

She asked why that made a difference. He hemmed and hawed, then finally said he didn’t know. She asked me. I did the same thing. It shouldn’t matter. But in this case, it did. Maybe there’s something going on with her external drive’s boot sector, but I didn’t feel like trying to explain what a boot sector is. Maybe it would work with the drive plugged into a different USB port. Maybe not. Not having the drive plugged in at all when the system is booting works like a champ though.

The moral of the story is that sometimes things that shouldn’t make a difference do make a difference. I used to see weird quirks like this all the time. I think PCs are a lot less quirky today than they were in 1995 or even 2000, but we haven’t reached the quirk-free phase yet. I just don’t run into it nearly as much since I do so little desktop PC work anymore, and there’ve only been a couple of different models I’ve had to work on in the last year, and corporate policy doesn’t allow us to plug anything but a keyboard or mouse into the USB ports. USB malware is a thing, after all.

But I’ve even seen USB gamepads interfere with the start menu. When in doubt, unplug anything unnecessary from your USB ports.