Thanks for all suggestions guys.
I solved it. Off course, I know about the possibilities of typing the IP address, but that's not an option for wife and kids.
Anyway, I solved it by editing the hosts file on each machine. It still wouldn't work untill I disabled the damned WinXP firewall on each machine. I wonder why M$ call windows user-friendly, aargh.
I feel great, outwhitting M$ for a change ;D