I just retested it with one of my old games, and A6.6 Commercial runs fine on Windows 7 64 Bit for me. I tested both the development and a published version.
There are several factors that can make your game crash on Win7:

- failure to install the latest DirectX 9c version. Even though windows 7 comes with Direct X11, you might still need to install the newest DirectX 9c version to run A6. For A7 and A8 I know that this is neccessary for sure. See if there is a "d3dx9_30.dll" file in your game directory. Try deleting it if it is there or moving it there if it isn't.

- trying to write files into the game folder (e.g. standard SAVE_DIR or WORK_DIR). Windows 7 only allows installations to alter C:/Program Files, not running programms. For a quick test, you can right click the exe and select "Run as Administrator", this will allow the game to write again. See if this changes anything.

-Are you using any DLL plugin? Make sure all the requirements are installed (OGG DSHOW filter, VC++ redist (x86 versions!), etc)