We ourselves (Winhost) are not the distributor of PHPBB. That is something you will need to download from their site. http://www.phpbb.com/about/?sid=57e80bccd901a5347c201efee121dda9 However, it should be compatible on our system.
I quickly read some of the procedure to install ImageMagick and it looks like it may need a direct installation to the server. Because we are a shared hosting environment I'm afraid we cannot support this. This is because it can have an adverse affect on all the other accounts we host. You may want to contact ImageMagick directly and verify if they have a version that can run on a shared hosting environment using a Windows 2008/IIS 7 platform.
You may be able to bin deploy ImageMagick (though admittedly I haven't heard of anyone doing it), but my guess is, even if you could, it probably wouldn't work very well due to resource restrictions. A Winhost site either has 100MB or 200MB of memory allocated to it, depending on your plan type (100MB Basic, 200MB Max and Ultimate). In my experience using ImageMagick on a unix server, that's not going to be enough memory. Unless all you're working with are very small images like avatars, etc. But if you try it, let us know how it goes.