I'm having a similar problem with a conexant internal modem.
Am running Mandrake 9.2 and trying to install a driver for it...When doing "Make install" it runs through some commands and then stops becuse of an error......
"KERNELSRC does not point to a proper directory ( /lib/modules/2.4.22-10mdk/build ) . Stop."
The "build" directory doesn't exist and from what I understand its trying to find Kernel header files??? not sure where these are?? any ideas??
The driver I'm trying to use is available from the followin URL:
I think in your case though ru2raj it might be worth trying kppp and seeing if /dev/modem or /dev/ttys0 ( or even s1,s2 etc ) work, as I had it once before on a different system and an earlier release of mandrake where it was meant to set the modem up on /dev/modem , but actually only worked on /dev/ttys0, don't know to this day why...but it worked and thats all I really cared about..hahaha.
Sorry I couldn't be more help but as you may of figured out , I'm still a bit of a newbie to linux myself.
Good luck though