I know absolutely noting about OS4, but have had lots of Windows network troubleshooting experince in my lifetime. In general, the problems you're describing may be:
1. One of your computers may not have the proper subnet mask. This is the 255.255.255.0 or 255.255.0.0 number in your TCP/IP settings. Double check that they're all the same. Home networks usually will use the 255.255.255.0 setting, but your config may be different for other reasons.
2. Does OS4 have a firewall? This may prevent ping and Samba responses.
3. One of your network adapters may be set at the wrong duplex setting. This enables two-way communication, but more often than not it is not properly auto-detected by network hardware. You may want to find out how to enable or disable it on both systems via software settings. (Ooops, just re-read your post. Scratch this if you're going wireless, it only pertains to wired connections.)
Good luck...
:-D
