DirectX 10 is part of the Windows Vista OS and can't be removed unless you repair or reinstall the whole Vista System. But 10 is not a full version of DX. You still need the 9.0 runtimes for games and applications.
Run the 9.0c installer and it will install all the needed runtimes and files so that you can run program that are for 10 or for 9.0.
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