The first time I had to see my neighbour I dutifully rang the bell at the front double doors. Eventually, she surprised me walking across the front walk behind me. "Oh, we never use those doors. Everyone knows the other door is our 'front' door."

Replacing a door with a window and removing a porch could be costly. I'd just put a neat sign on the door directing traffic where you want it.

Thank you Worthy. It's not that I don't want people using that door, I just want the room more...I don't know, comfortable as an entry and more flowing into the kitchen/the rest of the house. Not quite a mudroom, I already have one of those off the garage. I'd post a picture if I could figure out how.

I'd post a picture if I could figure out how.

Open a photo sharing account on a free service, such as PhotoBucket. Upload your pics there, then download the link here.

For the pic above, I didn't even leave the house to snap it. It's downloaded from Google Streetscape. Notice their watermark at least twice.

It's obviously impossible to picture without a picture. However, your situation seems to call for (luckily) less expensive and intrusive solutions.

It seems like a waste of LR floor space to reproduce an entry, coat closet and other architectural features of a main entrance when you already have one. Why not simply direct people to the correct door?

I have seen a few houses where there is a front porch alongside the the main door. Some folks simply furnish the porch like a sitting area, then drape a single decorative chain (such as wrought iron) across the door or entry to the porch. I've seen people put potted plants across the porch entry, as well. It also helps to single out your other door, your real front door, with a different paint color, more dramatic or more formal plant material, and prominent doorbells and house numbers. None of this costs very much.

I agree with the posters who said to somehow direct people to the correct door.

Your description reminds me of my neighbors house. They have a large original "front" door that they do not use (it actually has a sofa in front of it on the interior side), and the "real" door is a side entry.

If it were me, I would put something decorative and obstructive in front of the door you don't want people to use. Like a largish potted plant and some decorative statues. Maybe one of a laughing elf with a finger pointing to the true entry door. :-) If I was faced with two doorways, one with a path obstructed with potted plants and one clear, I'd walk up to the clear one.

I know exactly what the OP means. I know of a house, whose secondary door is the first one along the walkway. The secondary door opened into the family room with the coat closet way away from the door. The main door is much further down the walkway, so direct people to the main door is not practical. Also, if you have to carry the groceries through a much farther front door, that is not practical either. Besides, family members used the secondary door and dump their coat right by the door because the coat closet is too far away. I often wonder how I would "fix" the situation too. Find a place for the coat closet inside the room? turn part of the porch into mud room? find room for coat closet in the garage if it near by? move a secondary door to a better location so you can put in a closet?

Do you use the secondary door at all? If not, maybe fence or wall it off to have it look like a pato, rather than an entranceway.

I agree with jakabedy-some kind of railing or half wall. A quicker and less expensive thing that I also am a fan of is custom iron outdoor signs. They are called estate signs I believe if you google it, and you can simply engrave "main entrance" with an arrow pointing left, or "use main entrance".
It looks like you have a planting bed in front of the door that you can stake the sign in and it will look elegant. I had a sign made saying "dogs on property" next to a statue of a german shepherd at my driveway entry so that my guests will know to slow for the dogs, and to discourage any walk in solicitors ;)

I'd put any sign near the secondary entrance: "Service Entrance".

Is it possible to emphasize the main entrance -- a larger, more formal door, a pediment and flanking pillars?