As chabig said, both machines need to have compatible network addresses. And YOU have to assign them. It's under the Network settings on your Mac, just use the numbers he gave.
On the Windows machine, it's a little more difficult. At least Windows 98 had networking built in. The question is, does your Windows machine KNOW that it's being networked? Thinking back into the deep, dark past, I still can't remember exactly how things in Win98 are displayed, but here's a rough guide: Open the Control Panel and select the Network icon. It may be under an Internet icon, depending on how your particular computer is set up.
Now, select the TCP/IP protocol and click on the Properties button. Click on the "Use the following IP address" radio button, and enter the numbers chabig gave for the PC. In the Default Gateway box, put the Mac's new (manual) IP address.
Now, the
easiest way to do this is to buy a cheap router and let it handle all the "this computer's address is..." stuff for you. But that's just me...
