dll error at opening sibelius6.exe

[Hippie]

Hi,

When I want to install sibelius 6 on my computer it says it can't find the xerces-c_2_6.dll file. I've downloaded the file and tried to install the program again, but it says the file isn't a valid windows copy. I've tried other download links too, but all the same errors.
How to fix this problem, any ideas?

greetz