Interesting reading thread. I think many experiences and advice shared here are very good.
It is rather hard to know what would be a good solution, unless some or all of the constraints are known. These include, if the camera can be changed due to company policy, how much the person setting up the system knows about computer, etc., and how much is the budget, even if money is not a constraint for the computer itself.
Setting up a new computer to handle an outdated system is likely not recommended.
Newer cameras have higher resolution, providing real evidence, not just blurry mess, and the night mode is excellent.
I used to set up a wired based security camera system. I ripped them out later on, because wireless is simply superior.
I understand the privacy and hacking risk. In that case, I would avoid system that don't let you manage the cameras, and upload data onto the cloud. The only hard part is the encryption from the camera to the receiving unit. Is the encryption and video format proprietary?
Talk about memory lane, from coding in Cobol and assembly to working with HP Unix system, where I had to convince a customer to let me download and build a big specific compiler package for that particular system because the mainstream package doesn't have a patches that it needs to work. Luckily, they agreed. A big security risk.
I also recall managing a Solaris system for the US Senate. Each time the OS or software needs updated, it's a big hassle compared to Linux or Windows.
Now, I run all my systems in Linux and MacOS. I only use Windows when preparing taxes.
I built a few system before, from general purpose to gaming.
However, as many other have said, I also use used system. Workstation class system is very good. I own mostly laptops. They use much less power than desktop. They take very little space, have integrated keyboard, mouse and display, and of course, portable.
Workstation class laptops are powerful and expandable. Mine can handle 32 GB of memory easily. They also have some good expansion capability. The USB ports also help a lot with expansion.
For SSD, I run only on SSD on my main system without problem. Newer SSD software distributes out the writes, so that a same spot is not hit more often, and ended up trash the drive. However, with video content are big, and there is a lot of writes, it maybe good idea to have 2 drives with 1 SSD for the OS and 1 spinning drive for the data, with periodically backing up to another (3rd) spinning magnetic drive, using RSync for example or whatever appropriate (as some have pointed out).
Talk about a used computer vs new vs custom computer. A used or new computer often don't have standard ATX case. So if the motherboard dies, then you need to buy a same motherboard as the old one or very similar. A generic/custom computer case can accommodate most motherboard. Other than that, they are very similar. You may need to hunt down drivers for custom system compared to reputable brand name system.
Tricking a system to think the fan is working, such as by using a chip and not a real fan, will fry the system in a short order. It is the heat not removed from the system due to failed fans that cause other components to fail.
