Hi.. not sure if this will help, but I had the same issue on a brand new out-of-the-box machine from Dell. Inspiron 5521 / Win 7 Pro
Installed Office 2013 as usual but was getting same activation error. I uninstalled & re-installed, but would not activate. Finally, I used MS "Fix It" and that cleaned something out (sorry, wish I could be more specific, but it ran quickly, opened a DOS
window, went through it's business and at the end of it, I re-installed Office for the third time, and the activation worked fine.
So, if you can, try uninstalling it again.. and then run "Fix It" to see if it will clean up whatever it needs to. I hate the fact that I can't be more specific here by being able to tell you exactly what Fix It did, but at least it was able to allow me a
new clean(er) install of Office and get it to activate.
My suspicion is that there was something set or installed on the original image that was causing it to error, as the initial installation of Office with the computer right out of the box wouldn't activate.
Here is a link to the "Fix It" page.. read, see if any of it applies.. then if you want to run the "fix it" app (which is what I ultimately did), you can find the button for it near the end of the page.
Good luck - report back...
http://support.microsoft.com/kb/903275
http: / / support . Microsoft . com / kb / 903275 (remove spaces)