You’ll need a Windows computer to run HCA on. HCA isn’t a hog, so pretty much any reasonably modern computer will suffice. HCA runs very well on a 10-year-old Celeron processor 1 GB ram XP machine. Used machines have gotten so cheap (i.e. EBay, Craigslist) that there’s no good reason to skimp here. You can easily find a Windows 7 dual-core machine with 2 or 4 GB for under $100. The size of the hard drive isn’t so important, nor is having a dvd burner. An ethernet port is required but I’m unaware of any computer that doesn’t have one.
I tried running HCA on a laptop – it’s smaller, uses less energy, has its own battery backup. But I have had reliability problems after a period of running 24×7. I guess laptops just aren’t geared for that. So get a desktop, and buy a UPS.
The brand isn’t too important, but you want something that will run reliably. My preferences are Dell, especially the business-class Optiplex series, and Lenovo. Windows 7, either Home or Pro, either 32 or 64 bit (although if you will be using HCA to control other types of equipment you might want to stick to 32 bit, for driver issues). I’ve never run HCA on Windows 8 or 10. XP runs fine, but is no longer being supported, sort of.
There are 2 bios setup details that you should be aware of. You will want this pc to be able to run without a keyboard and mouse, and you will want it to restart automatically after a power outage.
A keyboard and mouse and monitor would also be needed, at least to get started. You probably will be wanting remote connection capabilities and Teamviewer seems to be the best free program for doing that.
The only other hardware you might be needing is an external hard drive, large enough to back the system up on. You do back things up, right? A wireless adapter, probably usb-connected, might be a good addition, depending on your network.