at this point it's been days of tinkering with configurations, i'm getting close to returning the 750ssd to newegg and buying a 730 just to get rid of this headache. I really want to make the 750 work but this is just so frustrating!
Have you tried with CSM option enabled in BIOS?
the MSI Gaming 5 bios has no CSM.
I appear to have figured it out.
Under the "advanced" section in the bios, there's a sub group called Intel Ready boost or some such. Once enabled a number of other options appear, including the ability to set boot from IDE to AHCI, allowing booting from NVME and changing default boot to PCI-E first.
I don't know why it's buried under some obscure section instead of under CSM as notated in the intel installation guide.
Using these settings I was able to get it to cold boot into both windows 10 and windows 7 with GPT format. I'm using it with windows 7 now and it has been stable all day.
Ugh, when I woke up this morning the PC would not cold-boot into the 750. not only that the drive was completely missing from windows explorer when I booted into my old SSD.
I was able to restart and the 750 eventually showed up, but any time I did a full power down the 750 would disappear. Despite proper configuration, the bios would throw an A2 error (boot device missing) and then eventually boot up the old SSD.
I've RMA'd the 750 and will update once I have a replacement.