Hello,
I remember using a PC Tel modem with Mandrake 9 about 18 months ago, and it was a case of compiling the driver from source - I think that unless you can find an RPM, that's what you'll have to do, too.
I don't know where you obtained your driver from but for reference, here is the link that I used -
http://linmodems.technion.ac.il/pctel-linux/
Using the command line and compiling from source really isn't too scary - don't be put off. Before you start though, do make sure that you've got the development tools (GCC, automake, autoconf, etc..) and kernel source installed on your machine - check your distro disks.
Then check out the documentation that comes with the driver - I've got it in front of me and it's fairly comprehensive.
An additional, and excellent tutorial in compiling, installing and setting up this driver, including troubleshooting, can be found at -
http://www.peacefulaction.org/sayamindu/pctel.html
Hope this helps and have fun!
EDIT: Nearly forgot to ask - what kernel are you running? The driver works with 2.2.x and 2.4.x but I'm not sure about 2.6...