I live in a 1990's townhouse. There are 5 (perhaps 6) phone jacks throughout my home. I want to convert all but one phone jacks to Ethernet jacks. I checked the phone box on the outside wall and found Ethernet cable is used for phone connection. So technically I should be able to convert. But I have no idea where to start. In the meantime, I also found there is one telephone box inside my garage. Two phone lines are connected to the box in the garage, the grey one goes to a phone jack in the garage, the blue one (cat5e) goes up through the wall/ceiling, and runs through the exterior wall, all the way to a room's outside and then drills through the wall to a phone jack.
Any information on how to do this landline to Ethernet line conversion?
You would need to determine which line is the one you want to keep as a phone line, then terminate all the other lines with an Ethernet jack at the wall, and a proper Ethernet patch panel at the central cabinet. Here’s an article to get you started.
Any idea on the phone box inside my garage? What's that? Why I have two, one outside one inside. The inside one seems pretty simple.
Without a description of where the wires might go, and any connections there may be, the only thing I can think of is it is an extension. As your description suggests it is a direct connection between a jack in the garage and one in a bedroom, without any other connection. Is the garage jack is an extension from the bedroom, instead of from the telephone cabinet? Is there another connection to the bedroom jack other than from the garage?