The generic keys are not for downloading, they are for installation only. For the retail downloader you must have a retail key. It will not work with an OEM license. See my other video here for details:  More details here: [URL] 
Hello,   I had purchased a Dell Inspiron 14z Ultrabook with Windows 8 pre-loaded on it. I have misplaced the manuals that came with the ultrabook and I now need to recover my hard disk back to it factory settings. I have already taken a backup of all my personal data. I called Dell support and I've received mixed messages from them. The first time they told me to continuously press the F12 key on system start up and then select 'Repair Computer' from the menu that is displayed. Unfortunately the menu shown on pressing F12 doesn't have such an option. They then told me to continuously press the F8 key on system start up and that hasn't worked either - The start up sequence carries on uninterrupted all the way to the login screen of Windows 8. If I go into Disk Management within Computer Management of Windows, I can see 6 partitions against my 500gig HDD (I haven't created any partitions of my own since I purchased the laptop). The first 5 are hidden partitions without a drive letter (an EFI System Partition, an OEM Partition, 2 Recovery Partitions and a Primary partition). So I know recovery is possible but I'm just not able to do it. Can someone please help me? Thanks!
Unable to Recover Dell Inspiron 14z Ultrabook to Factory Settings