Using Win 2000 you need a special program for IR Support, as MS Win 2000 does not supports IR and there is no patch available from MS. You need to purchase a program f.e. here:
http://www.extendedsystems.com/ESI/Products/Wireless+Connectivity+Products/IrDA+Windows+Applications/Product+Detail/IrCOMM.htm
Using ME or 9x you need to activate IR communication: START SETTINGS CONTROL INFRARED - options - enable IR. Also check the other options.
Next step is to get a modem driver from Motorola. You wont be able to use you mobile as modem without driver. Download it from MOTOROLA and install the modem via SETTINGS CONTROL ADD HARDWARE SELECT FROM LIST MODEM DONT DETECT HAVE DISC. Normally the downloaded files should also have something likean installation help or a readme file describing what to do.
Hope this will work. rgds.