you've got a so-called 'winmodem' or 'software' modem. these things can be absolute pigs under Linux. A driver is available from -
** But ** I noticed you're using Mandrake 10, so I'm assuming you're using the 2.6 kernel. I don't think drivers at the link above will work with 2.6.
I'd do a bit of Googling, but you might find that you don't get anywhere; in which case, I'd suggest you look at an external modem instead - they're much easier to get going.
Oh, and for the record, to set up a dialup connection (or any network connection for that matter) in Mandrake, you're better off using Mandrake Control Centre - you can configure everything from there.