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Windows XP left Microsoft support in April 2014, but it has never quite disappeared. It still drives measuring instruments, machine tools, till systems and legacy business software written for it and never ported since. Chkey.ch supplies XP keys for precisely those cases.
Home Edition and Professional are both available. Professional is the one that handles domain join, Remote Desktop and file-level permissions, which is usually what a workshop or a laboratory machine needs. An XP system should be kept off the internet, or isolated on its own network segment.
Your key is emailed within 24h, with an Swiss invoice.