I don't run Windows, but in my Linux system, if you right click the item you want to view, a menu pops up and I select open with other program and a list of programs shows up.
When you select the player that you want to use, Qucktime for instance with a *.mov file, there should be something to select that says "Always use this program to open files of this type.
Do this once for each type of file ( *.mov, *.avi, *.wmv, etc) and you should be all set, UNLESS, when installing a new program, you do not UN-CHECK the box that says make this the default program.
Basically what I'm saying is you do not want a default anything in your system.
You can still use the same program to view all your videos, provided a codec exists, but select the program once for each type and you should be all set.
Windows software makes assumptions and automatically changes settings in your system which can lead to security risks and confusion.
Hope this helps.