How can I create a script to run at system startup that does following operation:

Log in as root
Start Xine
Exit Xine
Log out root

The reason I need to do this is, because my video card wont work properly until I have started xine as a root so, that xine atemps to use vidix as video driver. (vidix -option won't actually work correctly, but for some weird reason everything else works after I have attempted to use vidix as a root).

I have also tried to update video drivers, but I haven't been able to get runlevel 3 to work either so...

You'll need to install sudo and configure /etc/sudoers:
- add the unprivileged user you use: "User_Alias XINE_USER = (insert account name here)"
- add the commands to run: "Cmnd_Alias XINE_RUN = /path/to/xine --plus --any --args"
- allow user to execute commands as root w/o asking for password: "XINE_USER LOCALHOST=NOPASSWD: XINE_RUN"
Save, close. Now make a script (or add as alias to their .bashrc), executable by the unprivileged user: "sudo /path/to/xine --plus --any --args". * If you have problems getting this to run please post actual error messages.

Couldn't you just put the commands in the /etc/rc.d/rc.local file. That way the commands are executed at boot time? The commands are executed as root. So if the command for xine is /bin/xine your /etc/rc.d/rc.local file will have entried like this.

/bin/xine
kill -all /bin/xine