The story is very old news though, this deal was struck on March 5, 2000 as part of a $200 million deal to make GPUs for Microsoft's original Xbox console. Microsoft likely wanted this right to prevent a console competitor from acquiring NVIDIA's GPU technology.
The message has appeared in the risk factors category of all of NVIDIA's quarterly and annual filing since the deal was struck, but it appears no member of the press ever stumbled upon it, until now.
On March 5, 2000, we entered into an agreement with Microsoft in which we agreed to develop and sell graphics chips and to license certain technology to Microsoft and its licensees for use in the Xbox.Source: Hexus
Under the agreement, if an individual or corporation makes an offer to purchase shares equal to or greater than 30% of the outstanding shares of our common stock, Microsoft may have first and last rights of refusal to purchase the stock. The Microsoft provision and the other factors listed above could also delay or prevent a change in control of NVIDIA.