I’ve been doing a bit of work on Mandriva recently, and I always forget that there are two places you need to change the host name before it “takes”.
in /etc/sysconfig/network add the following line:
HOSTNAME=hostname
Where hostname is whatever you want the computer to be called.
Then in /etc/hosts just add the hostname after localhost on the first (and probably only) line in the file. It should look something like:
127.0.0.1 hostname localhost
Where again hostname is the name of the computer.
Do this, reboot, and all should be well.