Where can I download the modem driver for a LifeTec LT9399 Notebook
PC? Serial Number 09N1019274. The operating system is Windows XP Home
edition. I do not know the model of the modem. I've tried to look.

Here's the main company :

Medion
http://www.medion.de/

If you click on 'service and support', you will then see a paragraph
in the middle frame that says "Treiber & Updates" - click on link that
says "mehr".

Enter 9399 in the form field for 'MD/LT Nummer'.

There are no drivers for Windows XP, but at least you know the chipset
is now PCTEL, who was bought out by Conexant some time ago.

To locate more information, we would need the manufacturer of the
modem and not the chipset. But it's a great start!

If you can look into Control Panel > Printers and other Hardware >
Phone and Modem Options, you may be able to see the modem make/model
listed under the Modem tab.

Let me know if you find anything else that may assist.

SgtCory