(Woow what a funny title!)
Some Silverlight 5 Toolkit users send me mails about this error message:
Error 1 Compile error -2147024770
(0, 0): error : Unknown compile error (check flags against DX version) (myfile.slfx)
To correct the problem, you just have to install the latest DirectX Runtime:
This error is generated by the Silverlight effect file compiler which wants to use the DirectX Effect compiler and don’t manage to locate it.
The DirectX Effect compiler is located in a library called d3dx9_xx.dll. The “xx” part may vary according to the version of the DirectX SDK used (in the case of Silverlight 5 Toolkit, we used the June 2010 version which relies on d3dx9_43.dll).
The problem is that this library is not installed by default on Windows (but a lot of applications installed it). That’s why you may be required to installed the DirectX Runtime which comes with all versions of the library.