GTR2 is one of the best racing simulations out there, to obtain a free serial (valid for online play) go to this address
Enter your email address in the field "E-Mail-Adresse"
Check the checkbox below, I don't know German but it shoud be about third parties sending you commercial offers (maybe some german goger could confirm)
Finally Click on "Seriennummer anfordern" to receive the serial number in your email
See you on track!

So basically, here's your serial but you need to accept that we distribute your emailaddress to anybody that asks, so that they can each send 5 spam messages a day?
Fuck.
That.
Shit.
At least create a dummy email that you're never going to use again if you sign up for this.

thats the exact kind of thing that dodgeit was designed for

Just tested, you can also request a serial without checking the infamous checkbox. It works :)
Also mailinator.com can help

what do you do once you have said serial?

I don't know you must downlaod game client from torrent I think? :P

the text reads

In case anyone was wondering about having to compare a computer image, my translation is as follows:
"I agree with the fact that the Axel Springer AG or her partner enterprises inform me from now on by e-mail about interesting offers and products. I can revoke this approval any time by writing to Computerbild Online Dienstleistungs-GmbH, Axel-Springer-Platz 1, 20350 Hamburg, or by e-mailing datenschutz@computerbild.de."
But yeah, easier not to check the box :)