Here is a step-by-step guide for a safe, self-made "AIO" USB drive:

Mainstream support ended in 2018, but extended support for Windows 8.1 officially ended on . However, many embedded systems and enterprise environments have paid for Extended Security Updates (ESU). For offline PCs or specialized hardware, 8.1 remains a viable choice.

Updating a single AIO image with the latest security rollups is faster than servicing half a dozen separate ISO files. Technical Hardware Requirements

Before installing, verify your computer meets the minimum system requirements. Microsoft's official specifications for Windows 8.1 are as follows:

Allows deployment on older 32-bit hardware or modern 64-bit processors from the same menu.

Modern UEFI firmware often only natively boots 64-bit media. Fix: Enable CSM (Compatibility Support Module) in BIOS or use a 32-bit boot manager.