I'm sure no one was "forced" to sign the contract, but by not signing it and agreeing to Microsoft's terms, you could not distribute Windows and other Microsoft products with your computer..
Not quite the same thing IMHO. By not signing the contract and doing what Microsoft wanted, since it was the de-facto standard at the time, you were pretty much kissing your PC sales business goodbye..
Look, anyone can make the offer MS made. If they price it low enough, they could get some takers. It was a smart move, because it meant that a dominant player would have growing market share among manufacturers who worked with them, but it would only work out if the product had traction -- otherwise, dealing with MS would just be paying Bill Gates to watch you fail.