Try the following link it worked for me
http://www.presentermedia.com/blog/2012/08/i-cant-open-a-powerpoint-presentation-in-2010/
To resolve the issue of opening an individual file, please follow these steps:
1) Locate the file on your computer
2) Right click the file and see the dropdown box which appears
3) Look to the bottom of the dropdown box and select “Properties”
4) In the “Properties” Window, you will see several tabs, the first of which should be “General”. Select this tab if it is not already selected.
5) At the bottom of this window you will see “Attributes” and “Security”. Next to the word “Security” is a description stating “This file came from another computer and might be blocked to help protect this computer.” and a box labeled “Unblock”.
6) Click “Unblock” , then OK.
7) Re-open the file by double clicking it, or opening it from PowerPoint’s “File” menu.
Note: Once you’ve Unblocked a file, the “Security” label under the General tab will disappear. This is normal and to be expected.