Windows 7 does not have native support for NVMe SSDs. You will thus need a driver to get this going. Microsoft released an update (KB2990941) that is purported to provide such a driver.
Hope his helps,
This message was posted on behalf of Intel Corporation
There are some steps you need to take in order to install Windows® 7 on this NUC with the SSD 600p, please take a look at the picture attached.
This information is available at Frequently Asked Questions for Intel® SSD 600p/Pro 6000p Series
NVMe.PNG 41.3 K