Common reasons for not adding a second NIC are:
You don’t have any open expansion slots in your computer
You don’t have any spare IRQs
Your computer doesn’t support IRQ sharing (for PCI NICs only).
You have an iMac! (Go here for more info on iMacs.)
USB 2.0 Ethernet Network adapters allow you to connect to a hub or switch to communicate with other systems on the network. USB 2.0 to Ethernet Adapters are compatible With Windows 98/98SE/Me/2000/XP. You can share your Internet connection or just transfer data between PCs in different rooms by using standard Ethernet Cat5 twisted pair cabling. Windows XP standard drivers do seem to work decent enough and with USB 2.0 there are even less installation and set-up issues, than with pervious versions of Windows OS. There are excellent help guides and how-to’s for using USB Ethernet Adapters with Windows XP, 2000, and ME here.
USB to Ethernet adapters & Win 98
If your computer has a USB connector, and you’re running Win98, you can use a USB to Ethernet adapter to create a separate subnet for your LAN, just as you would with a second NIC. There are a few things that you should note before you go this route
Remember that USB 1.1 is a shared 11Mbps bus. If you are already using a number of USB devices, you might not want to use a USB-Ethernet adapter, since you might get poor transfer speed.
There are mixed reports on using two USB-Ethernet adapters on the same computer. Many users have been unsuccessful, but there are successes. Let us know if you find a combination that works!
There is a known problem with computers running Windows 98 SE that use >350MHz AMD processors, and USB controllers from Via Technologies (you can check the maker of your USB Controller using the Device Manager). You need to download and run this Microsoft update.
There may also be problems with other computers that use the Via USB chipset. Check this Via page for driver updates.
Unfortunately, USB has problems just like Plug and Play and some adapters just don’t get along with some computers. If you run into problems installing a USB-Ethernet adapter on your computer, try a different manufacturer’s product before you give up on the technology!
USB to Ethernet adapters & Win 95
Quick note on trying to run USB on Win95. I haven’t tried this, but supposedly you can download driver updates from Microsoft. However, from everything I read, upgrading to Win98 is the easiest way to add reliable USB support to your computer… assuming you have USB ports on your machine!
USB to Ethernet adapters Manufacturers
USB to Ethernet adapters are available from many manufacturers and I’ve included a short list below. Note that these come with Win98 drivers only!