I don't know how to do that.
You have mandriva, where I think the init script you want is /etc/rc.d/rc.local
So, you need to become root, open that file with your favourite editor, and add a line like this to the very end of it:
su - yourusername -c "cd /home/yourusername && vncserver :1 -geometry 1024x768 -depth 24"
Save the file.
What this means is "Become the user "yourusername", change to that user name's home directory, then start the vncserver on display :1"
When you reboot, the vncserver will be started.
To connect to it, use the command vncviewer nameofcomputer:1