For those of you who might be considering whether or not to register your expensive Photoshop software, do it. Especially if you're prone to believing you've put the serial number in a safe place and discovering otherwise at the wrong damned time. Normally, I don't register shit. In this case, fortunately, I broke my habits, and that is why Photoshop Elements is back up and running on this machine.
Yet More Technical Difficulties
Of course, as someone who favors open source software (OSS or Free OSS, FOSS) my first preference is to avoid software with serial numbers altogether. They make the sort of tale Dana tells nearly inevitable. Expensive, useful software is likely to be in use for many years. I'm sure there are folks out there still using ten-year old versions of AutoCad, for instance, running on computers so old that they don't even have network cards. What's worse, for large organizations, keeping track of individual licenses for software, which the serial numbers represent, can be a nightmare. So they're best avoided if at all possible.
Unfortunately, there are going to be exceptions. Sometimes, only a particular piece of software will do the job in an adequate way. So, you pay, and you have to deal with the serial number problem. Worse still, some software installations require that you also have a string of numbers and letters called a "key" that is tied to that serial number before you can install the software. Standard practice among software vendors is to put that serial number and key, if any, on a separate piece of paper that will inevitably be lost.
For those occasions, I have some simple, but nearly foolproof advice. The most effective way to hold onto the serial number is to write it on the CD or DVD your software came on. If you don't have a Sharpie TM felt tip marker or something like it, buy one. They're handy for writing on lots of things, as this article demonstrates. Use your Sharpie to write the serial number on the label side of the CD/DVD. If there's a key that goes with the serial number, record that on the CD, too.
Let me emphasize that you should only write on the label side of the CD. Writing on the shiny side will make the CD useless.
I'm assuming, of course, that you're not "lending" this software CD to your friends. If you do that, you should definitely not write anything on the CD. Let them find their own serial numbers. Really. Vendors check for duplicate serial numbers, and if you are caught having the software with the same serial number on more computers than you're allowed by your software's license, they might sue you. But as long as you're not violating the terms of your software license, then the reasons the software vendor didn't put that serial number on the CD have nothing to do with you.
If you lose the CD, you can't install the software anyway. Software companies sometimes go out of business, or are bought out by companies that don't care whether customers who are using five year old versions of their product have their serial numbers or not. If you have the CD, and it has a serial number (plus key, if there is one) on it, you have everything you need.