[bluedan]

ATM, there's no need to install DirectX 9 on your computer unless you own one of the new NVIDIA FX cards and most likely you don't.
For the rest of the non-priviledged it does not improve your video system performance, AFAIK, since its main new features are only available if your graphic card supports DX9. Though Microsoft introduces a new video renderer engine that includes video mixing capabilities and thus may be the reason why bsplayer refuses to work.

I urge you to read carefully installation notes before installing new software!
I know it's the old song, but in case of DX, if you upgrade you normally cannot switch back, the system simply refuses to install lower version number DirectX nor were you able to uninstall it. See, easy way to screw your system.
Fortunately, there were some freaks to come up with a way to uninstall DX. I recommend to use this with care for it is not authorized by M$!