Ryoma writes, well this isn't exactly necessary but i thought you may be interested . since there are lot of people like myself that had problems with DX RC0 or 1.
this little application lets you uninstall DX 9 or any bogus Directx installations .. what it does is ask you for your winXP cd and restores DX 8.1 files from the disc it worked great for me so hope its usefull for you
Download: DX9 Uninstaller
News source: Techconnect