  You need to call Dell Technical Support. However you can also use a Digital River .iso as instructed here:  More details here: [URL] 
My Alienware x51 r2 did not come with the windows 7 install disc and I can't request another one using Media Dispatch Form because I am out of warranty. What is the best way to get a Win 7 disc from dell? My computer will not start in the system repair mode for some reason.
I need a Win 7 CD but am out of warranty