Windows 7: Who can I contact if my legal Windows 7 key is blocked from activation

I purchased my windows from digital river but because I have changed my computers hard drive multiple times, I had to reactivate it. It seems, Microsoft has blocked my key because of activating too many times. Who can I contact to get it unblocked?

Microsoft.

How to contact a Microsoft Product Activation Center by phone

I have already contacted activation center but they said they dont have the authority to unblock a key.

What is the exact message you receive? Have you read this thread?

Windows 7 Activation problem; activation key blocked. - Microsoft Answers

To properly analyse and solve problems with Activation and Validation, we need to see a full copy of the report produced by the MGADiag tool
(download and save to desktop - http://go.microsoft.com/fwlink/?linkid=52012 )
Once saved, run the tool.
Click on the Continue button, which will produce the report.
To copy the report to your response, click on the Copy button in the tool (ignore any error messages at this point), and then paste (using either r-click/Paste, or Ctrl+V ) into your response.
- **in your own thread**, please
Please also state the Version and Edition of Windows quoted on your COA sticker (if you have one) on the case of your machine (or inside the battery compartment), but do NOT quote the Key on the sticker!
How to Tell - Home