When showing a slideshow in PowerPoint 2010 through Remote Desktop, the screen might come up black. By disabling hardware graphics acceleration you can get the slides to show normally. To do this, go to File > Options in PowerPoint and select Advanced. Then check the Disable hardware graphics acceleration option to fix the problem.
Also you can temporarily black the screen by pressing the B button on your keyboard. If white suits your presentation more, you can press the W button on your keyboard.