The Radeon 9800 Pro Secondary Windows driver refers to a specific driver for the secondary graphics processor or secondary display output on a system with a Radeon 9800 Pro graphics card, which was part of the ATI Radeon 9000 series released around 2003. The Radeon 9800 Pro was a high-performance graphics card for gaming and multimedia, supporting DirectX 9.0 and offering excellent graphical performance for its time.

If you're using a multi-monitor setup or a secondary graphics card that involves the Radeon 9800 Pro, the "Secondary Windows driver" likely refers to the driver that allows Windows to detect and properly utilize the secondary display or output function of the graphics card.