The case is not separated into two individual compartments: there are large areas for air to flow freely from one compartment to another.
The panel below the PSU is perforated so that a PSU with a horizontally positioned 120mm fan would have enough fresh air.
The top (or, rather, leftmost) expansion-slot bracket is secured with a screw. The other brackets have to be torn off. It is not good because you won’t be able to put them back once you have removed them. The expansion cards are fastened with screws, just like the mainboard.
There is a lot of room in the bottom half of the case. Even with all the components inside, including a dual-slot graphics card, and with all the cables laid out, the interior was not exactly filled up.
Of course, the system case imposes a limitation on the height of the CPU cooler. My Zalman CNPS9500 AT did not fit into the AeroCool M40, so I used an Ice Hammer IH-3775 WV instead. I wouldn’t say that this limitation is too strict. Far from that, it is quite relaxed for such a compact enclosure. The cooler can be as tall as 110 millimeters (for comparison, the Antec NSK1380 does not accommodate CPU coolers taller than 65 millimeters). Thus, it is possible to use boxed coolers and you can easily find a quiet model.
When put together, the two halves of the chassis are fixed with two moving plastic levers located on the right of the top half.
When the top half is flipped back, it can rest on a special folding support. If you don’t use it, the top of the case, heavy with the hard and optical drives, can topple the whole case over.
The top half of the case is populated more densely than the bottom one. The back area is occupied by the power supply, leaving but a small channel towards the vent grid in the back panel.
A cage for two optical drives is located in the top left of the enclosure. The drives are fastened with screws on one side and with quick-fastening plastic brackets with prongs on the other side. This solution is easy to explain: the bracket’s turning handle does not fit in from one side. And on the other side of the drives, it is hard to use screws as you need a very short screwdriver to drive them in.
HDDs are installed into an individual cage. The protrusions on the side of the cage fit into a groove inside the system case. You can additionally secure the cage with two screws.
The cage is not positioned properly inside the enclosure. The HDD power connectors, when inserted, press against the back of the power supply so hard that I really worried they might crack. This can only be avoided by using L-shaped power connectors that are available with some PSUs or adapters. You can’t turn the HDDs around so that their connectors faced the opposite direction (the front panel) because there is even less room there. The manufacturer might have solved this problem completely by changing the point of fastening of the HDD cage, but it did not and the user has to face the problem himself.
The cooling of the HDDs raised my concerns immediately. They are located in the blank corner, right above the system fan. There is a seat for a 60mm fan opposite the HDD cage, but such fans are not freely available and often prove to be loud.
Assembling a computer in this case is unexpectedly easy. The proper component layout (save for the above-described problem with HDDs) saves you the trouble of doing acrobatics and showing the nimbleness of your fingers as you often have to while putting together a compact PC. The M40 looks nice when assembled. The cables can be laid very neatly. Take note of the free space behind the graphics card. You should not worry that a long graphics card may not fit into this enclosure. As a result, the AeroCool M40 can accommodate a rather advanced configuration notwithstanding its compact size and unusual form-factor.