Despite the name, a desktop computer does not need to be on a desk. The big towers PC would fit well on the floor. But you should think about ventilation and dust so your game PC does not overheat.
The carpet can block the air flow
Modern PC cases are usually not completely flat on the bottom. They have feet so their bottom is off the floor a little. There is airflow during the case. All PC cases have fans that release hot air and valves that allow cold air access. Some cases even have extra intake fans that further facilitate cool air.
So it should still work. If you place your case on any thick plush carpets, the carpet may block some of that airflow. This is very bad if the air is to flow into or out of the computer through the bottom of the case. It is bad even if the air does not flow into or out of the case here, but if the computer lowers in the carpet a little, the heat can be built up due to lack of air flow.
Of course, if you have short carpet on the floor, the computer may be sitting on that carpet with a lot of airflow below. And if you have no carpet at all, it's not a problem. Your computer will just be at home sitting on a flat floor as it would on a flat desk.
Before putting your computer on the floor, be sure to think about the airflow. Avoid placing your tower PC on thick carpet. If the carpet is a problem, consider placing it on a platform or standing on the carpet. You can buy rolling places for this particular purpose, which also makes it easier to move the desktop around. Heck, even if you put a piece of wood on the floor and lay the computer on the wooden platform, solves this problem, although it may not be beautiful.
Your computer will suck in more dust on the floor
Your floor almost certainly has more dust, hair and other detritus than a desk or table. This is important – the fans of the computer draw in the air and blow out the air. These fans can suck dust, dirt and other debris into the computer.
This happens wherever you place your computer. Even if you have your computer on a desk, you sometimes want to dust it with a little compressed air. But your computer will probably suck in more dust and debris when it is on the floor. Dust gets in the way of cooling your computer, and it will run hotter if it needs cleaning.
It is easier to dust and clean around a computer that is also on a desk. If it's in a corner, how often should you move your computer case, vacuum and dust the cables behind you? It is easy to shut off cleaning and have dust built up where your computer sits.
If you keep your tower PC on the floor, remember to dust it out regularly – probably more often than you need if you keep it on a desk. It depends on how dusty your floor is, but you may want to check out a few months. You should also remember to clean around and behind the case to avoid dust build-up.
Apart from that, the floor is fine
Problems with ventilation and dust – both of which lead to overheating – are the main reasons why geeks usually afford to place a desktop computer on the floor. But if you have both of these things under control and have thought through it, is it really a problem with leaving the computer on the floor? No not at all. It is good.
The floor can even be preferred in some situations. There is a good chance that you have more space on your floor than your desk and placing your tower on the floor will free up some space. Some people with heavy PC towers may be worried about those who fold on a desk and fall on children or pets.
Of course, your circumstances may be different. If there is a risk of flooding, your computer is safer if it is away from the floor.
All of these considerations are most important with gaming PC or workstation that generates a lot of heat. If you have a low power desk that does not generate much heat, ventilation is not as big a problem. Modern, lightweight desktop computers are often small boxes that can easily fit in a corner of your desk, anyway.