what script handles X startup

[Marcel Janssen]

Hi,

I guess the title says it all. I simply can't find the script that handles the 
whole sequence of starting up X.
Mine seems pretty messed up so I want I have a look at it. All scripts I read 
so far are fine but my installation starts the wrong desktop (the correct one 
is specified in prefdm and .Xclients, .Xclients-default but it choses to 
start always XFCE).

Is there any log file that can tell me what is done ?

Regards,
Marcel