to the forums.
It is not reccomened to switch between USB and ethernet as each time you would need to turn off the modem before switching the cables.
You can also NOT use both the Ethernet and USb ports together on the modem as that will not work.
If I was you I would buy a wireless broadband router. Make sure it is not an ADSL one. They cost about £30-50
Your new PC would connect to it through it's ethernet port or a wireless card. Up to you.
Your Windows 98 machine with only USB ports then has a few options.
You could buy a USB wireless card that plugs into your USB slot and communicates with the router.
Alternatively, if you have a spare PCI slot in your PC, stick a £8 ethernet network card in and connect by ethernet to your router. OR Put in a wireless PCI card.
As for Ethernet cables, this is the type of cable you need when connecting computers to a router.
Ethernet Straight Cable, see
HERE