NTVDM Error

I recently came across a challanging problem attempting to install software on an NT 4.O client. When I went to start a setup program as soon as it executed I received a WOW NTVDM error which locked up the computer. I applied Microsofts fix which said to replace the command.com file with a working machines, which I did. This seemed to work at first by allowing me to install two applications. Then when install Iomega Zip drive software it came up again. Can anyone help solve this? The machine is running SP 6a.