Remote linux installation

Hi Masters ,
Can any one help me with remote installation of linux.
 I want to do linux installation remotely, under my control. A blank 
machine ( shipped directly  to one of my client  from dell) is  on 
public network.
Now I want to do linux installation on that machine. I have heard about 
doing this by tptp server and PEX  configuration , but i think (correct 
me if i am wrong) it will help only if , the machine is on local subnet, 
not on public.

So is there any way to do this ??

Any suggestion is welcome !!

thanks in advance ...!

--Alok