You need to disable PlugNPlay with the second driver disk in DOS. To do that you can use a Windows 98 diskette to start the machine without CD-support. Then put the second driver disk in the machine and run install. After confirming the license agreement you can choose configuration. Do not choose auto install or auto configuration. That will set your NIC PNP.
The second driverdisk you can download from www.3com.com.
It's an packed .EXE you have to unpack to diskette.

Goodluck.