Or just download the ISO file with Win 7 directly from Microsoft: https://www.microsoft.com/en-us/software-download/windows7
Use the serial number from the sticker on your computer. When done, download drivers from http://h20566.www2.hp.com/hpsc/swd/public/readIndex?sp4ts.oid=3912020&lang=en&cc=se
I used this method on my Z800 to get a clean installation of Win 7. The other reason is to avoid the very long installation times when using HP recovery media.
