Please ensure your Windows 7 has installed all the latest Windows updates.
Install the latest ver of Photo Gallery. Try right clicking on the Photo Gallery Program and Run as Administrator.
Also check the Picture Folder (or the folder you have pictures) right click > Properties and under Attributes uncheck any check box and Apply. Also check the Security tab and see if you have the adequate permission.
Check if you are trying to access pictures from another User's folder, copy/move the pictures to another folder & see if you can access.
From Photo Gallery , File > Include Folder and Add... the folder you are trying to access and then check if it allows.
But before trying these, please ensure you have updated Windows 7 to latest updates and have the latest ver of Windows Photo gallery.