i do use powerpoint 2007 and 2010, and i am able to open a ppt file with both versions...
Try creating a new user account. If it works in the new user account, then the old user account may be corrupted.
http://answers.microsoft.com/en-us/w...5-d98dbe96e327
http://windows.microsoft.com/en-us/w...ses-by-default