GTA 4 serial number HELP!

[Kratenser]

I bought GTA4 for the PC yesterday, and now after having finally installed it, I cant play it. When I try to, a menu pops up asking for my Serial Number. Only thing is, I cant find the damned thing. I bought it second hand, and this was what was inside the box:

Game CD's 1 and 2
Survival guide to liberty City
Liberty City street map
The GTA 3 instruction manual (what the hell?)

I cant find the Serial number anywhere inside the box and now im confused, where the hell is it?
Did anyone else have this problem?? Is there any way to bypass the activation and just play the damned game?

Please help if you can, i want to get playing!!!!

 

[mad825]

it's on the back of the 'On liberty' booklet.

If you want to bypass the DRM then search through *ahem* less discreet websites