The Intel® SSD 750 Series is a PCIe NVMe device. Booting from it requires uEFI, 64bit OS and NVMe driver.
If the original installation was done using a UEFI installation source, and with UEFI boot enabled, then the migration may work. The issue is that most Win 7 installations are not done in UEFI mode.
If the source installation was from a SATA drive or RAID volume, the OS will not be able to boot from the PCIe drive after the migration. If this is the case, a fresh install is recommended.
For more information, please review the Intel® SSD 750 Series - Frequently Asked Questions (FAQ).