Here’s some useless information. While doing some spring cleaning last weekend, I encountered a box of 5.25″ floppy disks. These disks had been tucked away in the back of a closet, and hadn’t been touched in well over a decade.

I quickly thumbed through the 100 or so disks in the box. I was amazed at what a great job I did of backing up software installation disks, and what a bad job I did of preserving data. I had a complete set of installation floppies for Windows 3.0. There was an installer for PFS: Professional Write, which was the first word processor I used. There were lots of disks of downloaded software. I remember anticipating the loss of Internet access upon leaving college, and I had ftp’d, downloaded, and archived a lot of stuff I thought I might need.

In the whole lot, I found five disks of data that were interesting enough to keep. The rest of the box went in the trash. Now the challenge began. How do I get the data off? I’ve written before about the problems of data format obsolescence. I headed for the box of old computer junk under the work bench in the basement.

I dug out an old 5.25″ floppy drive. There were actually two in the box, and I grabbed them both in case one didn’t work. I went back upstairs and popped the cover off the old P3. I figured I could just disconnect the 3.5″ floppy and connect the 5.25″, and I’d be in business. It quickly became apparent that this wasn’t going to work. The old floppy drives had card edge connectors, and the slightly less old floppies have pin header connectors. I needed an older cable. Back to the basement.

By some miracle, I had the cable I needed. I plugged it in, booted up the machine, and everything was fine. Windows XP didn’t know what this drive was (it thought it was a 3.5″ floppy), but it could access it without any problems. I put in a disk that I didn’t care about, and it read it with no problem. I put in one of the data disks, and copied the data onto the hard disk easily.

Then I put the second disk in. Windows complained that the disk wasn’t formatted. I guess having a bad disk in the box isn’t such a big surprise. So I tried another one. Same thing. As it turned out, all four of the other disks I wanted data from were “unformatted”. I put the first disk back in, and it read fine.

Then, I took a closer look. The first disk was a high density disk. The others were all double density. The high density disks stored 1.2 MB of data, while the double density disks only stored 360 KB. I remember spending a lot of time in the 1990’s explaining the difference to people who were trying to fit a lot of data on a little disk, and I was glad to see the floppy die entirely. But it was curious that the high density disk worked and the double density ones didn’t. After confirming this with another high density disk, I headed off to Google.

As it turns out, Windows XP cannot read floppy disks that do not have a media descriptor byte in the BIOS parameter block of the boot sector. Lots of old floppies have this problem, and in my case, it looks like they’re all double density disks.

The “official” workaround from Microsoft is to use a disk sector editor to modify the media descriptor byte on the disk. Just change these two hex digits on the disk, and you’ll be fine, unless you do it wrong, in which case your data will be irrecoverably lost. Since that’s a little beyond my confort level, I think I’ll just dig up a computer running Windows 98 to recover the data. Sometimes, working in a school has its advantages.