This isn't fair, I am not a beginner with computers I just don't know where to post this question. Whenever I download new applications like photoshop or a new video player it changes the default application for my media. How do I change the default applications for my computer.

This has to do with associations. Associations are one of the most powerful features of Windows. It allows you to open a file, just be selecting the file without opening the program first.

Most programs will create an association with the file formats they create. Some will allow you to select this during the install. Some do it without notice. You need read up on associations on how to find them and set them in Windows Help.