You're looking for a download link for Windows Server 2012 R2 Foundation ISO, specifically for Dell hardware.
Because Foundation is OEM-only, standard retail or volume licensing ISOs often will not accept a Foundation-specific product key. To reinstall, use these official methods: Windows Server 2012 R2 | Microsoft Evaluation Center windows server 2012 r2 foundation iso dell download hot
Dell OS Recovery Tool: You can use the Dell OS Recovery Tool to download a recovery image specifically customized for your server. You will need the Service Tag of the machine to verify eligibility. You're looking for a download link for Windows
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