XPS 15 (L502X) - HDD Dead - Where do I get the Windows7 DVD to install the new HDD?

Hi 
I have a XPS 15 / L502X from 2011 - HDD died now - And I installed a SSD disk - BUT where/HOW do I get the Install Windows DVD  for my PC.
Cant get it from the old disk - I made a Rep disk from the old installtion - and I DID think that this contained the Windows and drivers for my DELL.
But it doesnt!?!? :-/

So How do I now install the new HDD on my dell? Anyone?

BR
René