I have three Macs. One is the G3 iBook that I bought back when Apple finally delivered the first practical desktop Unix. It was very nice, but these days it mostly just runs my Rosetta Stone language software. Current OS: 10.4.1. Hostname: Cyberdoll.

The second is a dual 1GHz G4 tower attached to a 20” Cinema Display. It’s still quite nice, and does a decent job with Photoshop and other applications (most recently World of Warcraft). Current OS: 10.4.1 and 10.4 Server. Hostnames: Arrin-Ken and Tai-Tastigon (Server).

The third is a 15” 1.25GHz G4 PowerBook. It is the center of my existence, holding all my email, projects, ripped CDs, games, toys, downloads, etc. Current OS: 10.3.9 (mama didn’t raise no fools). Hostname: Slots.

At work, there’s a Windows machine that I use for scheduling meetings and filing expense reports. Nice hardware, pity about the OS.

I have purchased quite a few songs from the iTunes Music Store, and all four of these machines were authorized to play them. When I was rebuilding Arrin-Ken last week, I deauthorized it, wiped the disk, installed a fresh OS, and then reauthorized. iTMS says: 4 machines authorized.

Today, I decided to deauthorize the Windows box at work. I just wasn’t using it for music much. When I was done, I logged into the store from my PowerBook and checked the authorization count: 5. Not good, so I checked it from the Windows machine: 3.

Belatedly, I realized that I might have actually done things in a slightly different order when creating Arrin-Ken, namely wiped the disk and then deauthorized it (it had multiple partitions, and only one had ever run iTunes). The authorization count was correct afterwards, so I didn’t worry about it. But I checked it on the machine that had just been reauthorized, and now it seems that the answer you get depends on where you’re standing when you ask.

Officially, doing things in the wrong order uses up an extra authentication slot:

Make sure you deauthorize your computer before you upgrade your RAM, hard disk or other system components. If you do not deauthorize your computer before you upgrade these components, one computer may use multiple authorizations.

But the count was correctly four when I checked it from that machine after the upgrade, and is now correctly three when I check from the Windows box. The obvious thing to do is to attempt to authenticate a completely different machine (say, the Windows laptop at home that only exists to make VPN connections to work), and then see how many authorizations they all think exist.

Worst case, I can exercise the once-a-year wipe option and remove all of my current authorizations, real and imagined. But that’s overkill if it’s just a glitch.

Update: glitch. All of my machines now report the correct authorization count.