See here to apply Dell OEM SLP activation using the ABR program: [URL]
Hi there, In our company we have an Optiplex 3020 and have reinstalled the Windows 7 from scratch as I installed an SSD. - I extracted the product key with a software in the preinstalled windows 7 (pro x64). As you know, there's no longer COA sticker with the key. - I downloaded an image and installed windows 7 pro x64. - I inserted the extracted key but windows says it's invalid so I can't even have the telephone option to validate the key. My guess is that I was using the wrong W7 PRO x64 image but I downloaded the official ones, so it should be fine. Could you let me know how I can activate Windows? Thanks!
Serial number invalid on Optiplex 3020 - Windows & won't activate