Once Microsoft unbundled the browser they started using their monopoly position to force OEM's to include the browser or facing increased costs for the Windows

Once Microsoft unbundled the browser they started using their monopoly position to force OEM's to include the browser or facing increased costs for the Windows OS, and since and OEM couldn't sell a computer if it didn't have windows installed it left the OEM no option but to add the browser the OS. Microsoft's grip was so tight that they prevented IBM from bundled OS/2 on IBM pc's, windows was alwasys installed and OS/2 needed to be a separate line item.