{"product_id":"boot-error-an-operating-system-wasnt-found-after-changing-bios-boot-mode","title":"Boot error: 'An operating system wasn't found' after changing BIOS boot mode","description":"\u003cp\u003e\u003cstrong\u003eThe problem:\u003c\/strong\u003e After switching between UEFI and Legacy\/CSM, firmware no longer finds the installed OS.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eSymptoms:\u003c\/strong\u003e Boot message: OS not found\/no bootable device after BIOS change; disk still detected.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eLikely cause:\u003c\/strong\u003e OS installed in UEFI\/GPT but firmware set to Legacy, or OS installed in Legacy\/MBR but firmware set to UEFI-only.\u003c\/p\u003e\u003cp style=\"font-size:13px;color:#6b7280;\"\u003eCategory: Boot \u0026amp; Startup · Difficulty: Moderate · Windows: Both\u003c\/p\u003e\u003cp\u003eDigital knowledge-base article delivered as an instant download after purchase — no physical shipment.\u003c\/p\u003e","brand":"LVL1","offers":[{"title":"Default Title","offer_id":46984989737157,"sku":null,"price":23.99,"currency_code":"SGD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0809\/1831\/5205\/files\/lvl1-37.png?v=1790190908","url":"https:\/\/www.lvl1.store\/products\/boot-error-an-operating-system-wasnt-found-after-changing-bios-boot-mode","provider":"LVL1","version":"1.0","type":"link"}