Microsoft had contracts with all of the OEMs, if an OEM wanted Microsoft's OEM pricing, they needed to pay for a Windows License with every PC they sold.
Buying a PC without Windows meant buying parts and assembling it yourself. Wasn't too difficult, but you were SOL if you wanted a laptop.
Yes and no. Name brand computers tended to come with Windows. But there was a printed monthly magazine called the Computer Shopper that had ads for mail-order stuff of every possible description, and you could buy a motherboard plus the rest of the pieces without Windows.
Right about that time period, copy protection of the Windows CD's was altering the equation.
Yeah, most of the big online ordering sites (Dell, Gateway, etc) would only let you get a copy with Windows. It was a huge deal when Dell started letting you buy "naked" PCs.
Buying a PC without Windows meant buying parts and assembling it yourself. Wasn't too difficult, but you were SOL if you wanted a laptop.