I downloaded and installed the "official" user end version of Dx9 from microsoft.com. Works ok, no problems but no boost in FR with my machine anyway. Still staying at 86 with refresh rate 90 on Sony Monitor. However lowest I've seen FR fall was 67 vulching an air base smoking with many aircraft visible.
AthlonXP2400
ASUSA7V333 Mobo
256 DDR PC2100
GeForce4Ti4600
Windows98SE