Plugin doesn't load on some systems

I am developing a networking plugin for the A7 game engine. I have released a beta version, and some people are reporting problems with it. It seems the engine cannot load the plugin dll on their system.

When running dependency walker on their system for my plugin, it says dwmapi.dll and efsadu.dll cannot be found. After installing VC++2005 Express (what I used to develop the plugin with), it works fine.

The strange thing is that on my system, dwmapi is not listed as a dependency. This is probably due to a different version of ws2_32.dll (winsock library; depends on many dlls including dwmapi.dll and efsadu.dll).

I did some searching and found out that dwmapi is a windows vista only dll; "Desktop Window Manager API". efsadu.dll is a windows XP pro dll for file encryption or something.

I also read that both of those dlls are only loaded when they are needed, so this "dependency" should not result in problems on systems that don't have that plugin.

Still it can't load my plugin. Anyone have an idea of how to solve this or where to even start looking for a solution?