Jima, if you know the brand and model number of your computer, you can just select it with the drop-down boxes on crucial's homepage.
The only reason that you would need to download the scanner is if you don't know the make and model of your computer.
If it's a dell, it says it right on the front (Ex. Dell Optiplex 330).
So, you'd just select dell, then optiplex, then 330 and it will tell you exactly what you need.
If you're still running a computer with 128 MB of RAM, purchasing more will INDEED speed up your computer, but it might be time to purchase a new one! They're really cheap nowadays!
I know this doesn't have anything to do with your question, and that you aren't even looking to put more memory into your computer, but I thought I'd give some help on the crucial site.
As for your original question, no I haven't seen that problem yet. That's probably because I don't know anyone that has dial-up still, nor one that uses a machine with less than 512MB of RAM.