Support for Windows 7 is limited: The SD card is disabled when Windows 7 is selected in BIOS Setup.
Also, Windows 7 Embedded is not on the supported operating system list for your NUC.
This message was posted on behalf of Intel Corporation
That’s correct; these Intel® NUCs support SD cards only in Windows* 8.1 and Windows® 10. I’m sorry there is no support for SD cards in Windows 7.