The most common mistake when building a PC

Building your own custom PC from parts is not only a hobby, but for many enthusiasts the only way to build the gaming rig they really want. Not only is it cheaper that way because you aren't paying the prebuilt PC manufacturer for the work (at least in theory), but you can more easily choose which parts you want in it, according to your budget and needs. Many PC gamers wouldn't even consider buying a prebuilt system (not even if you can choose the parts for it).

PC building is quite a hobby in itself, and not surprisingly there are tons and tons of tutorials out there especially on YouTube.

There is, however, one very common mistake that most people who are building their first PC make, or even their second or third (until they are bitten by the consequences of the mistake). What's worse, this very same mistake is often done in most tutorial videos as well, sometimes even when the video is made by a person who should know better. Even very technically experienced people making PC building videos seem to often make this mistake.

What is this mistake?

It's building your PC completely and fully, all the way to the last screw and zip-tie... before turning it on for the very first time to see if it boots up.

Oftentimes it works just fine. Too many times, however, it won't POST, or there will be some other problems (such as no image of any kind).

Sometimes this is because of incompatible parts. Even to this day (and perhaps especially in this day and age) there can be components that don't work together. The motherboard might not support that particular type of CPU (at least not without a BIOS upgrade), the RAM sticks may have some kind of incompatibility problem with the BIOS, the CPU, or even with each other (modern RAM sticks tend to sometimes be extraordinarily picky, sometimes even not working with other sticks of the same model from the same manufacturer, but manufactured in a different assembly line in a different factory) or a myriad of other problems. Maybe one of the components (like the PSU) was just bad and needs a warranty replacement.

Whatever it is, there's a good chance that you'll need to replace something in the PC... which often means taking the PC apart once again (completely or to significant extents). This may be especially so, and especially laborious, if you eg. have chosen a water cooling system, and you need to eg. replace the CPU, as this means pretty much taking everything apart.

Every experienced PC builder ought to know by heart that the very first thing you do when building a new PC is to first and foremost make an absolutely minimal build with the motherboard on the table, with the CPU and an air cooler and the RAM and GPU installed, and then connect the PSU and see if it POSTS. This way if there's something wrong and you need to replace something, the amount of work is minimized.

Some even may want to install the system's main hard drive and install the OS in it and see if it still works, before continuing to actually putting the motherboard inside the PC case. (This especially if you want to use a watercooling system, as you really don't want to have to take it apart immediately again.)

How many times have you seen this done in a YouTube PC build video, or even PC building tutorial? I have seen way too many videos where the author does not do this, even by people who should really know better.