ATi developer driver (for Win98/ME). It is reported as containing a new OpenGL ICD that is meant to increase OpenGL performance by around 10%-40% (not guaranteed) as long as the previous driver set used is completely uninstalled.

ATi Radeon 4.13.9017 unofficial beta driver for Windows 98/ME

driver dated 02/19/2002 (19th of February 2002)
OpenGL performance reported to increase by 10%-40% (not guaranteed)
older drivers must be completely uninstalled before installing this driver!
beta unofficial driver unsupported by ATi thus install only at your own risk!
for any help with the driver visit Rage3D forums.
Download this driver...HERE. (11.1MB)