WINDOW NT WORKSTATION

My computer came with Window NT Workstation loaded with network card and no modem. I got a modem installed and connect my phone to the computer. I tried to use the computer to connect to the Internet but return an error that COM port is not properlyconfigured. Now I don’t want NT but want to load Window 98. I booted the computer to MS-DOS but I can’t access my CD-ROM drive. What do I do to load my Windows 95 or 98.