"what about my modem ? its 56kb internal serial modem <motorola>"
Any external serial modem will work with any Linux distribution. Some internal modems will work and some will not. Some internal modems are complete modems just like external modems. Other internal modems have only part of the necessary circuitry to work. They make up the difference by writing Windows drivers which supply the missing hardware functions. Such incomplete modems are called winmodems. Your modem is undoubtably a winmodem.
Linux software drivers have been written for some winmodems, but not all. Linux drivers for winmodems sometimes work and sometimes don't. Three years ago I could not get my winmodem to work. I threw it away and bought a cheap external serial modem which has never given me any trouble.
Here is a link to an explanation of how to get a Motorola winmodem working:
If this is not the same Motorola model as your modem then use Google to search for a Linux driver for your exact model number. If you cannot find one then no one has written the necessary driver. If you find one maybe you can get it working.
Be prepared. Create a LifeBoat CD.