Hello.
Im used following OS:
Windows 7 Home Premium 64 Bit SP 1
Windows XP Home Edition 32 Bit SP 3

All the same, the stupid Use-Button has no function. In order from the Manual fall i back to the Game-Screen. But not happens and the Object don´t appear on the screen.

Help me please or this stupid game is worthless!

The "Use" function works in a bit unusual way. On the game screen click the object on which you want to use something, and then go to the inventory, select an item and click Use.

Thank you. Problem solved.

No problem :)
Enjoy the game.

I have the same issue as the original poster, "use" does not work with the camera so I can't take a picture of the blood. I tried clicking on the bloodstain then selecting the camera and "use" as you suggested, but the camera still doesn't appear in the main game screen so I can't use it. Is there something I have missed?