Are you trying have both machines connected at once?
If so, how are you connecting the Mac and the PC to the modem.
You can only connect ONE ethernet cable to the modem at one time. You cannot do Ethernet and USB at the same time.
All broadband connections are always on, unless you turn off the modem, so there isn't any configuration to do.
The usual practice for multiple machines, a local area network, is as follows:
Incoming line (cable or DSL)
Router (usually 4 port)
What configuration is yours
My current connection is to a Broad Band from BSNL on Windows XP. The connection is configured in such a way that the line is always on and need not connect every time. Done using the TCP/IP. Trying to replicate the same on my iMac, but with little luck.
Any suggestions would be welcomed