Even apparently simple tech improvements can go awry.

Recently I decided to download some fun programs, or "apps," to my iPod Touch.

The Touch is nearly identical to an iPhone — touch screen, Wi-Fi Web access, virtual (on the screen) keyboard — but doesn't include the phone. As a result, it can use apps from Apple's iTunes online store.

But first my Touch required an operating system upgrade, to version 2.2.1. Using iTunes on my PC, I downloaded the new operating system ($10) and two game apps (one $4, one free.) Then I hooked my iPod to the PC to install the new software.

That's when things began to go wrong.

To prepare my iPod for the new operating system, Apple's installer program began to back up its songs and photos, which I'd otherwise lose during the upgrade.

But an error message said the backup had failed. I tried again with the same result. The message also said that if I went ahead without the backup, the Touch's contents would be wiped out.

Now I was irritated. There'd been no warning this might happen, and no apparent reason for it to occur. But since I wanted to use apps on the Touch, and had already invested $14, I went ahead, knowing I could reload the iPod.

It took me a couple of hours to restore the iPod's contents and to add the new apps. Then I went to an Apple Store to ask what went wrong.

The answer left me wondering whether Apple's upgrade policy was a way of restricting what I did with my iPod.

My iPod backup failed because I hadn't enabled an iTunes feature called "sync" that automatically synchronizes the iPod's song playlists, photos and apps with those stored on a PC. With sync, adding or deleting items in iTunes will cause them to be added or deleted on the iPod the next time it's connected to the PC. Further, the iPod backup software I used doesn't actually copy songs and photos, just the device's sync settings. That way, iTunes can restore the iPod's contents after the operating system upgrade is finished.

That's slick, but it makes life hard for people like me who load the iPod from more than one PC. If I used sync on both computers, the iTunes on my desktop PC would delete everything loaded from my laptop, and vice versa.

Why did Apple create this unhandy backup scenario?

Clearly, it simplifies iPod back-up, if only for Apple.

But it also tends to limit consumers to using their iPods with a single PC if they want to avoid being wiped out during an upgrade.

Will that deter users from loading free songs from a friend's PC?

Just wondering.