Sharkfood said:DirectX is always backwards compatible with prior versions, so having DX10 also means you have full DX9.0, 8.0 and 7.0 as well.
You do not need (nor want) to install DX9.0 on a DX10 system as this is already present.
It comes out of the box with this.Nexevo said:As Zenosincks' links inform Vista does not run previous versions of DX it infact emulates them.
No you do not. Vista ships with this as part of DX10.So you will need to install DX9 and when required Vista will emulate it.