A few things that you can try:
- Check in your particles folder that you do not have any duplicates. These will end in _00, _01 , _02, etc. If they exist, you'll want to delete them
- Change your rendering subsystem. If it's possible to change it from the rendering system popup you keep getting, you can do so, or you can type in your prefered system in the ogre.cfg file in your FH folder
- Make sure there are no addons or mods that were installed improperly that is causing the game to crash.
- Right click on the game and chose "Run as Administrator"
Hope this helps!