connecting through a dsl modem ..

im using a windows xp sp2 pro edition .. i have a dsl modem ..
i can connect to it either through ethernet or usb
i use the ethernet for my laptop net access
and the usb for my pc net access
i would like to know how i could use both the ethernet and usb on my pc ..
i know it sounds wierd but plese do let me know
cause i can connect either through the usb or the ethernet . for example if i connect both the usb and ethernet to my pc i can dial either through the usb or ethernet but once usb is connected i would like to make a seperate connection and connect through ethernet. the problem im facing is that windows even in the second connection tries to access the modem through usb so where could i change the settings so that it can access ethernet and allow me to dial evn though im connected through usb ...