My problem is that the ISDN adapter does not work, I have build this PC with the adapter already installed. I installed Mandriva 2005 LE.
In short, as you can see from diags i add to this post my problem manifest with this line
[Can't open /dev/isdninfo or /dev/isdn/isdninfo: No such file or directory]

[root@hek ~]# service network restart
Shutting down interface eth0: [ OK ]
Shutting down loopback interface: [ OK ]
Disabling IPv4 packet forwarding: [ OK ]
Setting network parameters: [ OK ]
Bringing up loopback interface: [ OK ]
Bringing up interface eth0: [ OK ]
Bringing up interface ippp0: Activating device: ifcfg-ippp0
Loading global settings: /etc/sysconfig/isdn
Loading default settings: /etc/isdn/profile/ippp.default
Loading network settings: ifcfg-ippp0
Loading link settings: /etc/isdn/profile/link/myisp
Using profile myisp : IPPP-Default
Can't open /dev/isdninfo or /dev/isdn/isdninfo: No such file or directory in /proc/net/dev
Check ISDN hardware configuration [FAILED]

[root@hek ~]# lspci
...sniped...
00:09.0 Network controller: Cologne Chip Designs GmbH ISDN network controller [HFC-PCI] (rev 02)
...sniped...

The device like some others I tried all have the HFC-S, 2BDSO ISDN, CCDC0350E - Chipset E.G. IA1281P-STD from Planet

[root@hek ~]# uname -r
2.6.11-6mdksmp [Mandriva 2005 LE]