Years ago, I switched from Microsoft to Apple. I got a refurbished "Late 2013" MacBook Pro - loaded with a 15" Retina display, 16 GB RAM, quad core i7, SSD, Nvidia display hardware, etc. It far exceeds my needs as far as performance - I can run PhotoShop, keep 30 tabs open in Chrome, and it does not even breathe hard. And we also got a MacBook Air. Add to that iPhones, iPads and we were entrenched in the Apple "walled garden". This was something I had not envisioned, even after years of tinkering with Windows and living with blue screens of death, hangs, updates taking forever, and so on. Also - I have always been a proponent of open-source software, so the Apple embrace was something I had always poo-pooed. Anyway, I have not regretted it - the Apple stuff just works and the integration of iOS and MacOS is seamless. The only downside of buying older Apple hardware is that Apple drops support (meaning no OS upgrades) after several years. However, the 11-year old Macbook Pro soldiers on. I did finally replace the battery, which was dying.
However, I still wanted to have a Windows PC around for my workbench to occasionally play with software not available on Apple and perhaps run a VM host or Docker containers for non-Windows stuff like Linux . Not wanting to spend a lot of money (as usual) I looked around for a cheap way of getting something half-decent.
There are various ways you can approach this. For instance, a Raspberry Pi 4 will run Windows pretty well - if you can find one. Or you get one of those "micro" PCs like a used Intel NUC or even a cheap ARM-based TV box like the one mentioned in my article here. These options are pretty constrained in terms of performance and expandability, so I wanted to find something a little more useful.
I searched eBay and found an outfit called The Blind Center of Nevada. They take in donations of used computer equipment, refurbish them, and sell them to bring in revenue. Most of the workers are vision impaired and it seems like a worthy cause. They sell used equipment at very reasonable prices.
I settled on an HP ProDesk 400 G3 SFF (Small Form Factor - meaning it is very compact) built in 2016 so not too old. It was reasonably specced with an Intel i5 quad-core processor running at 3.2 GHz and 8 GB of RAM, 500 GB hard drive, Windows 10, 8 USB slots, DVD drive, and best of all, they were asking $62 shipped. The shipping alone had to be half the cost. I must have caught them on a good day because I see the same box goes for over $100 currently. It arrived in perfect condition and very clean cosmetically.
I had a 19" monitor, keyboard, and mouse left over from an old tower PC (about 20 years old and pretty useless - which went to the transfer station for recycling). Once hooked up everything worked, but it sat on my workbench doing little more than web surfing and looking up audio and electronic references. And it was slow compared to my MacBook. Too slow. The hard drive would shake, rattle, and roll at the slightest mouse click or whenever Windows felt it necessary. I then remembered why I disliked Windows. I did all the usual tricks to "optimize" Windows, but the main culprit was the slow hard drive.
I found an old 256 GB SSD I had in a box and swapped out the hard drive. I installed a fresh copy of Windows 10 from a USB stick. At the same time, I added another 8GB of RAM - I think it was $15 on Amazon. This box only has two SODIMM slots, so it is now fully populated. I could have boosted it to 32 GB, but it seems Windows 10 is pretty happy with 16.
Next up was the video hardware. Like many low-end machines, it has Intel integrated graphics, which steals main memory and causes contention with the CPU for memory access, so I got a used GeForce GT730 Nvidia PCIE X16 board on eBay ($18) to drop in the one available slot.
I then added a Sceptre 27" QHD (2K) monitor that has 2560 x 1440p resolution. It came with a Display Port cable, which was nice. I got it for $120 during Amazon Prime Days (it now lists for $179, so was a good deal). It is a very good monitor for the money - hopefully, it proves to be reliable. The built-in speakers are a bit anemic, but I will be adding external speakers connected to my USB sound interface (an old EMU 0404 USB that I also use for distortion measurements).
So now, while not a gaming machine by any stretch, it is a reasonable performer for under $100 (not including the monitor) - you may consider a similar approach if looking for a cheap second or third computer. I have been running Reaper on it to play around with music synthesis and recording and the large display makes it very usable.
I bought an inexpensive glass and metal desk (which turned out to be really nice) and added a newer wireless keyboard and mouse to make it more of a workstation. The little MIDI keyboard connects to the Reaper software via USB for toying around with music composition. Cheap little speakers from Amazon added decent sound from my old EMU 0404 USB audio interface.