Some Suggestion
To let all of your computer can see each others, try to install WINS server in your Homeserver. since you are using windows 2000 in your Homeserver, so i think that's simple to solve this problem.
For your password problem, if you don't want to enter password once you are trying to access other machine, you can use the same administrator password as well. For example, if your Homeserver use:
username: administrator
password: testing
so, you just simply configure your XP and windows 98 machine as the same password configuration. as a result, each of your machine can access each other as well.
other suggestion:
it is better to separate your koen and joris from the Homeserver as well because of security purpose. try to use other subnet instead of the same network. NAT would be the best choice here.