Ubuntu (7.04) doesn't find WinXP machine

[Jürgen Römer]

I have switched to Ubuntu and I'm happy with it. The only problem is the 
network. I have one Vista-computer, 2 XP:s and one Win98. The network is 
working through an ADSL modem/router. With only Windows-workstations the 
network worked fine (except Vista). The IP-numbers are given 
automatically by the broadband operator.

Now that I have an Ubuntu-workstation, it cannot find the other ones 
(occasionally it finds Vista, usually not). I have configured Samba 
according to instructions. I'm able to find the Ubuntu from the XP:s 
with the IP-number (which varies at least daily) , but I can't see the 
Ubuntu with the others in the "workgroup" window. From Ubuntu I can't 
find any other workstations no matter how and in which way I try.

In the Windows-workstations practically everything is shared. Ubuntu 
firewall is configured according to instructions.

It seems that the network is working on some level (XP finds Ubuntu with 
IP-number), but it is far from working satisfactorily.

What might be the problem?

In the following is my smb.conf file. I have used also another version 
based on the template smb.conf which is created by installation, but 
that doesn't work either

[global]
    ; General server settings
    netbios name = jurgen
    server string =
    workgroup = koti
    announce version = 5.0
    socket options = TCP_NODELAY IPTOS_LOWDELAY SO_KEEPALIVE 
SO_RCVBUF=8192 SO_SNDBUF=8192

    passdb backend = tdbsam
    security = user
    null passwords = true
    username map = /etc/samba/smbusers
    name resolve order = hosts wins bcast

    wins support = no

    printing = CUPS
    printcap name = CUPS

    syslog = 1
    syslog only = yes

   
; NOTE: If you need access to the user home directories uncomment the
; lines below and adjust the settings to your hearts content.
;[homes]
    ;valid users = %S
    ;create mode = 0600
    ;directory mode = 0755
    ;browseable = no
    ;read only = no
    ;veto files = /*.{*}/.*/mail/bin/

; NOTE: Only needed if you run samba as a primary domain controller.
; Not needed as this config doesn't cover that matter.
;[netlogon]
    ;path = /var/lib/samba/netlogon
    ;admin users = Administrator
    ;valid users = %U
    ;read only = no

; NOTE: Again - only needed if you're running a primary domain controller.
;[Profiles]
    ;path = /var/lib/samba/profiles
    ;valid users = %U
    ;create mode = 0600
    ;directory mode = 0700
    ;writeable = yes
    ;browseable = no

; NOTE: Inside this place you may build a printer driver repository for
; Windows - I'll cover this topic in another HOWTO.
[print$]
    path = /var/lib/samba/printers
    browseable = yes
    guest ok = yes
    read only = yes
    write list = root
    create mask = 0664
    directory mask = 0775

[printers]
    path = /tmp
    printable = yes
    guest ok = yes
    browseable = no

; Uncomment if you need to share your CD-/DVD-ROM Drive
;[DVD-ROM Drive]
    ;path = /media/cdrom
    ;browseable = yes
    ;read only = yes
    ;guest ok = yes

[MyFiles]
    path = /home/samba/
    browseable = yes
    read only = no
    guest ok = no
    create mask = 0644
    directory mask = 0755
    force user = jurgen   
    force group = jurgen