I had to reinstall Windows 98 and did so without apparent problem. I got the latest drivers for the integrated NIC (Davicom 9102) from www.davicom.com.tw
and the nic installed without apparent error.
However, when I try to access the file server (SCO UNIX - VisionFS) the download is glacial, when I don't get an "error 2 on drive ?" and the computer slows way down (20 - 30 seconds from clicking botton on the taskbar to seeing the button depress) and Prior to reloading windows this system ran just fine with the vendor supplied configuration (came with win98). It is a Pentium II - 450 with 384 Mb of ram. The System tab shows no yellow splotches other than one for the sound card, for which I do not yet have the drivers.
Another win98 machine on the network can access the server without problem.
The link light on the hub blinks irregularly, but only about once every 2 seconds instead of rapidly.
I don't have tools to snoop the network to see what is happening.