As Mark Pilgrim has previously pointed out, Windows has a half-life.

Every installation of Windows naturally degrades along a logarithmic curve until it becomes annoying, then unbearable, then unusable. Each successive revision of Windows has featured a slightly longer half-life. Back in the day, Windows 95 would last me about 3 months, while my copy of Windows XP has lasted me almost 9. I’m not bitter; when you realize that you’re measuring on a logarithmic scale, a factor of 3 improvement is really quite impressive.

Petty arguments about whether it’s a logarithmic or exponential curve cast aside, I think most of us have been there. I unfortunately got there on Monday evening, and so with a weary sigh, backed up my data, and rebooted from my XP install CD.

Got through the boring blue-screen bit:

Press D to delete this partition.
Now press Return to confirm deletion.
Now press L so that we know you really really mean it.

Sigh.

The next stage, as we’re all too painfully aware, is the copying of files onto the shiny new partition, then a reboot, and then the install proper begins, unpacking the OS from the .CAB files on the hard drive itself.

Except we didn’t get that far. After the initial reboot, my BIOS cheerily informed me that we had a problem:

Error Loading Operating System

I’d never seen that one before.

Fired up the laptop, and Googled for the error message.

The first hit was Microsoft Knowledge Base article #326676: “Error Loading Operating System” Error Message When You Restart Your Computer During Setup. Looked promising.

Make sure that you are using the latest BIOS revision for your computer. Contact the computer manufacturer to inquire about how to obtain and install the latest BIOS update that is available for the computer.

Er, nope. It worked yesterday, on exactly the same hardware, with exactly the same BIOS settings.

If you are using an IBM computer with an AWARD BIOS version 4.5x, visit the following IBM Web site:
http://www.storage.ibm…htm
Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.

I don’t think there’s a single IBM component in my computer. And the hard drive certainly isn’t an IBM model. And anyway, it worked yesterday, with exactly the same hardware!

So even Microsoft don’t know what’s causing it. Or rather, they think they know what’s causing it, but they’re wrong.

Anyway, through trial and error I eventually booted from a handy Debian Installer CD, and manually nuked the MBR on my hard drive. Retried the XP install, and all was well once more. The XP installer must have had a hissy fit and written me a dodgy MBR the first time around.

So, to sum up, the possible fixes are:

• (from Linux/BSD/etc) :
  dd if=/dev/zero of=/dev/hda bs=512 count=1
  (assuming the hard drive in question is /dev/hda, of course – don’t do this if you don’t know what it means)
• (from a Windows 98 boot floppy) :
  fdisk /mbr

The first one worked for me, but apparently the second will work fine as well. The Windows XP installer won’t write a new MBR if it thinks the current one is okay, so you do need to zero it somehow before repeating the install. Phew.

Anyway, perhaps the next person to Google for that error message will eventually find the solution here. Does anyone know how I can inform Microsoft that their Knowledge Base is incorrect/incomplete?