Did a clean install of Windows 7 from a used CD and now I cannot activate it.
I advocate you run the Microsoft Genuine Advantage Diagnostics Contrivance in normal mode (not safe mode) and copy and paste the results in a reply for further analysis:
Run the Contrivance and when it completes click the Copy button, open a set book file like Dress Up or Notepad and select Edit, Paste. You can paste directly into a reply here. Open a reply, right click and select Paste.