Reshade not working on MW2

I cannot seem to get my reshade to work on my modern warfare two, everytime i try to, i get the message, "The process cannot access the file '\MW2\d3d9.dll' because it is being used by another process." so i go into my mw2 file to look and i see a text document that says this,

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I am not sure what you are trying to do but whatever it is, you should try doing it while your MW2 is not running.