In 1997, Spyglass threatened Microsoft with a contractual audit, in response to which Microsoft settled for US $8 million.

According to McGeady, NSP threatened Microsoft because it was software at operating system level, while Microsoft believed they "owned software to the metal," (i.e., to the hardware level).

While Linux has several million devotees around the world, it holds a minuscule share of the operating-system market, and Mr. Warren-Boulton fairly laughed at the proposition that it threatened Microsoft.

The last chapter chronicles how the PlayStation 2 threatened Microsoft with upcoming multimedia and personal computer appliances promised in the post-PC era.

Microsoft's past success in hurting such companies and stifling innovation deters investment in technologies and businesses that exhibit the potential to threaten Microsoft.

Can they threaten Microsoft with a refusal to license Windows?

Would a Facebook/Skype tie-in threaten Microsoft?

Netscape once threatened Microsoft with a software browser that promised to be an alternative to its overwhelmingly dominant computer operating system.

In 2012, the company threatened Microsoft with legal action for infringing on "Metro" trademarks held by Metro AG.

The European Commission threatened Microsoft last week with fines as high as 3 million euros ($3.9 million) a day for failing to comply with the order.