Try using Shell Demo Player, its small and real easy to work, instead of opening Diamond Demo Player, selecting the demo etc. you just put all the Shell Demo Player files in your Soldat file and then open the demo files.
Put all files in Soldat folder.
Installation:
Download Shell Demo Player
Put all files in your Soldat file
1. Open RKLLu.vbs in notepad.
2. Replace C:\Soldat\ with path to your Soldat folder.
3. Save it.
4. Open sdm.reg in notepad.
5. Replace every C:\\Soldat\\ with path to your Soldat folder.
6. Save it.
7. Run sdm.reg and press Yes to add it to your register.