After putting my plans on hold for a few months, I am getting ready to proceed with buying myself a new desktop computer. I was set to get a tower case like all my others for the last twenty years, but I have hesitated. The first modern computer I owned, received as a graduation present twenty years ago, came in a horizontal case: narrower than a tower and square or almost square. I don't know what you call that form factor, and I don't know whether they're popular anymore, because I haven't seen any for sale on my electronics store sites. If they're still made, I would look into one of them.

Then I thought, is that because people can just lay a tower on its side, as long as the air vent faces up? Or is there some reason a tower should not lay horizontal? I honestly don't know. Would it interfere with the components working properly?

I have always liked the Shuttle PCs - black, cube-shaped, only one fan. I use one as my firewall.

There's nothing in a standard PC tower that cares about laying down. Even DVD drives still work that way.

Used to have several of these at work (as now most have laptops) that were on its side:
https://www.dell.com/en-us/shop/dell...n-3472-desktop

If you are building your own machine, I am sure you can find a case like this.

Thanks, that answers my question.

Hmm, I would probably want to stick with a standard ATX form factor, not a slim tower or anything else with a tighter working space. I'm clumsier than most people (coordination problems), so getting myself a smaller form factor is probably asking for trouble.

There is no problem for basic function whether a tower is upright or horizontal, so you have a wide range of choices. However the "laid down" cases that were popular for a few years way back in the late 80s early 90s are impossible to find, at least new. If you are seeking a different profile because of desk space you might like one of the cube cases though most of them are for very small form factor mobos. One just about to be released (8/1/2019) is this CoolerMaster - https://www.newegg.com/p/N82E1681111...82E16811119374.

BTW since we no longer have to deal with many teeny tiny pin jacks and sockets (like PATA and SCSI) size isn't as important as it once was with the single exception of cooling where compact = hotter.

What you originally had was a 'desktop case' that sat with your monitor on top of it, things moved on to having 'tower cases' that stood on the floor, then they reduced the size of them a bit & called them 'mini towers'. There are some 'small form factor' cases that are even smaller, but still quite large overall.

One of the reasons people didn't use them on their side, was because they were made of much thinner/flimsier metal, which wouldn't support a CRT monitor, but would normally be OK with a flat panel/LED/LCD monitor.

I prefer small, quiet computers, so I use SBC & SOC computers, & they also have the advantage of coming in very small cases, about 4"x4"x2".

Desktops are still available via OEMs, but cases are rare. HP for example still produce "convertible" tower/desktop PCs, mainly targeted at business users, usually in small form factor.

I'm not sure why home PC towers came about, but originally tower cases were for servers, but then desktops quickly started changing to tower format in the 90's. Probably a fashion / marketing thing based around the look and space saving.

They had cooling problems from the off. For the "full towers", the biggest problem was all the drive bays. If you populated a tower with a stack of 2 or more hard disks + 2 or more optical drives, that heat just builds up in that section of the case. Unlike a server case, most of the low end consumer cases were simply not designed to ventilate that area sufficiently.

Also I remember reading that the vertical motherboard position affected heat dissipation - i.e. heat not being able to easily rise up from the components (and the tangle of old 40 pin ATA ribbon cables not helping with that much either).

One of the components, but that nowadays isn't that important anymore, that has problems "on its side" is the CDrom/DVD drive(s), the disk HAS to lay on top of the tray OR the drive must support a caddy (a sort case the disk itself is first put into and then the whole case is put into the drive).
In the original desktop cabinets all drives were built-in horizontally, like in a laptop,
while in a (mini-)tower they rotated all bays so the drives STILL are horizontal while the cabinet is vertical.
BTW: this mounting is one of the reasons desktop cabinets were abandoned, because you only had 2 drive bays, my HP mini-tower has 6 (3 of 5.25" width (like DVD or tape drives, two "hidden" ones for 3.5" hard drives and one optional one for a floppy drive - empty in my case).

One of the coolest cases, both literally and figuratively, I've ever seen and owned (I have 2 of them) can be seen here ====>> https://www.newegg.com/p/N82E16811129145

As you can see they are "out of stock" at newegg so I don't know if they are still available but I imagine something like it surely is. They are all aluminum and very light, yet quite sturdy and have excellent airflow even when operated in "Cool 'n Quiet" mode. They come with 2 120mm fans installed - one at lower front, Input, and one at upper back, Output. They are also very compact but compensate for that by rotating the main drive bays 90 degrees so one does not have to insert drives by passing over the motherboard, which works with any form factor - full ATX or smaller. The harness with handle comes with it but is unneeded except for safe, solid transportation.

The only caveat is the size does restrict the use of high end video cards unless you check dimensions carefully. If you're a gamer, check measurements of the length of any video card you consider but this is mostly the above $200 range of cards. Most video cards with one or two fans fit just fine but those with 3 or more, are "iffy".

I had not realized until this thread that traditional "desktop" cases have pretty much disappeared from the market!

Since traditional desktops could be stood on their sides (I've done it without issue), I guess there is no reason to think that towers could not be laid on their sides, unless doing so might block the cooling vents. In my mind, that's a pretty big reason, so I'd check the placement of the cooling vents before deciding to lay that box down.

I work in an industrial setting. We have thousands of systems that are placed every which way. The only issue we ever had was one system didn't seem to read cd's correctly when on it's side. Otherwise the bits don't know up from down.

Speaking strictly as a home user and hobbyist, I haven't had this issue, as long as I've been able to snap the optical disk onto the spindle in the optical drive.

.....& for drive trays that don't have the spindle, just hold it against the drawer as it closes, worked for me no problem.

Doesn't work for mini-CD's (the 170 KB ones) as they will slide down anyway.
They're the ones that fit in the inner ring of the tray.

Beautyful. I haven't bought my case yet, so I'll see if I can find this case elsewhere.