The Font Store automatically loads rasterizer DLLs from \sys\bin\ on all drives at startup. The search path is soft to hard ( Y:, X:, W:, ..., C:, B:, A:, Z:) and if two or more files have the same name the first one found is used. This means that files in the ROM (Z:) can be replaced with files on user drives.
Rasterizers are identified by their signatures: the second UID is KUidOpenFontRasterizerValue and they have the extension .DLL.
To install a font rasterizer DLL: