Hi Pavel,
A couple of possibilities:
1. Are you running an NT Domain, or a workgroup? If it is a workgroup, are all of your subnets part of the same workgroup? Clients only see members of their own workgroup or domain in Network Neighbourhood, unless they click the "entire network" choice. If it is an NT domain,...
2. I assume from your post that your PDC is also your router. Is it the WINS server as well? Are all of your clients configured to use it, either by using global options 44 and 46 in DHCP, or by adding the address of the WINS server to each client's TCP properties manually, which overrides DHCP?
To verify this.....
3. Check your WINS database to see if all clients are listed, and if they are in the same workgroup or domain.
4. If you have multiple WINS servers, they will not exchange info automatically, you must set up WINS replication before clients registered with one will see clients registered with the other.
Keep me posted (peer mail). There are other possibilities, but this will get you started.
Ian