Question: I'm a computer technician and I have to reinstall computers of all brands a lot.
Now i'm looking for a way to make a ghost image for example for XP which I can install on all computers. Just like you do a clean install?

Can someone think of something what works?

Answer: 
Sadly, XP doesn't do that. Windows 7 is intended to work that way (one image, regardless of hardware), but with XP you need a separate image for each make/model.

The closest you can get is to set up an unattended installation that you can fire & forget. It'll still take longer than just copying over an image, but at least you won't have to interact & answer the prompts.
Sounds like you want a custom automated install. Creating a ghost image of Windows and expecting it to work right out of the box on many different arrangements of hardware is a pipe dream of all windows administrators.

Have a read through this example using *nLite*: <http://teamtutorials.com/windows-tutorials/how-to-make-a-custom-windows-install-w-nlite>

There are other tools for doing similar things, and this is precisely what people like Dell and HP etc do when making a windows installation for distribution with a computer (packed full of rubbish AV software etc)