Hi Bevo 3 welcome to sevenforums
I'm not sure what to say about your current problem seeing that you're developing software to utilize D3D. Anyway to state the obvious make sure the problem PC has the latest DirectX files. You might also check that your video card's drivers are up to date.
Also, if you're using the developer kit and the problem system doesn't have it installed that might be saying something about compatibility? Just a guess as I'm no developer, nor an expert on Direct X
By the way have you looked here DirectX Developer Center