You can reinstall MacOS from a backup using a USB drive.
You can reinstall MacOS from a backup using a USB drive.
You're facing a tough situation with your 2009 Mac Pro. Since you don’t have another Mac or a reliable Mac environment, you’ll need to rely on external tools and careful steps. One option is to use a bootable USB drive with macOS installation media, but you’ll need to source it yourself. Alternatively, consider using a cloud-based reinstall service or a third-party tool designed for flash drive installations. If you have access to a Mac, it would be easiest to perform the reinstall there first. Otherwise, you might explore online guides or forums that specialize in MacOS recovery from old hardware.
Press CMD + I upon startup to launch Internet Recovery. Alternatively, use CMD + R; it will boot into Internet Recovery if no operating system is detected. The system typically attempts to download the launch OS, which can be inconvenient when upgrading. On my mid-2012 MacBook Pros, this was Mac OS X Mountain Lion if I booted into Internet Recovery without any OS installed.
You can use a Windows machine (if available) to create a MacOS installation drive with a 32GB or bigger flash card. Simply press the power button while connected to the drive, and when the boot menu appears, select the MacOS installer from the flash storage. For a 2009 Mac, you'll only get El Capitan available. Just keep in mind this setup isn't ideal for modern use and will restrict your Mac's capabilities.
It’s possible you’re SoL because I recall a few years back encountering problems with older Macs lacking supported operating systems. Apple typically removes older OS versions that aren’t available for recovery environments.
Where should I find the right place to complete this? It seems like everything I looked at was questionable. I don’t need a Mac—I just want to build a Windows server PC. I’m on a tight budget and this is the most capable machine I have. What I really need is MacOS to transfer the hardware to Windows, since simply adding a Windows SSD didn’t work before.
Turn the mac on and press and hold the option/alt key down to select the boot device. It's a computer, so you need to find the CD/DVD with the OS and drivers for that computer or get a copy of the operating system and install it. You can also run linux on it via the same process.