Boot from HDD, run everything possible from SSD via PCIe adapter card

[MysticStylezzzz]

I cannot find any useful info online for this PC.. I got it for free and became interested in seeing how snappy I could get it to function. Well, I've tried different SSD's and CPU's and RAM, all pretty successful. But currently I have the original HDD back in which is a SATA 3 HDD and the board only supports up to SATA 2, and there's x1 and x16 PCIe slots.. well, the HDD is damaged apparently because I keep getting random errors with just about anything I try to install or update now.. so I have a Toshiba m.2 NVMe 256GB SSD on a Yateng adapter card (x4), which holds a SATA m.2 and an NVMe m.2 (only has the NVMe m.2 on it) and the computer sees the m.2, I can store and run programs and files from it, but it won't allow me to boot from it, which obviously is typical.. I'm about to get rid of the HDD and just boot and run windows (10) from a USB drive, and then run every single program from the m.2. my question is can I boot from say another HDD or flash drive, and then run windows itself from the m.2? I'm asking if I can BOOT ONLY from another drive and then run windows itself from the SSD? Have tried a few things without success but it was more experimenting.. I only want the thing to be able to boot since windows install manager says the m.2 isn't bootable.. so again, only want it to boot from the slow drive, and then run windows itself from the m.2. or can you only boot from the same source that windows is installed on? Not sure if I'm asking this right but... 

[WAWood]

@MysticStylezzzz 

I can think of a way that MIGHT work -- as I am using it to boot from one SSD and run Windows versions on other SSDs.

The product is known as EasyBCD and is available for free from NeoSmart Technologies.

It allows you to modify the BCD on one volume to add boot lines for Windows (and other) OSs on other volumes.

I have three SSDs in my PC, always boot from the same one, and am able to launch any of the other Windows OSs on the other volumes.

[MysticStylezzzz]

Oh awesome, thank you!! I'm going to have to try that!! It sounds like what I'm looking for! 

[SLEhrgott]

Hey thanks again for your help man!!! I ended up receiving a Samsung m.2 SATA pm871b I picked up for a few bucks today. Didn't expect it until Tuesday, so I have what I need now to get my computer work completed by tomorrow night. However, I'm still going to try that truck between these 2 SSD's since the NVMe {via PCIe slot) benched at just over 1500 Mbps (don't remember if that read or write specss) and the other prolly runs around 250 Mbps (haven't benched it yet and an just now finally installing Samsung magician to enable rapid mode and/or turbowrite. I've seen on benchmarks that turbowrite doubles days transfer speeds, and some.. my Mobo only supports SATA 2 but it'll be a huge improvement next to that edited HDD! I had a cm871 that was only running at sata1 for whatever reason and it was still a big improvement over the hdd at SATA 2 lol so 3gb\s paired with turbowrite and should ease my mind until I order all the components to build myself a super work station on black Friday. I just hern something to get my school work done, by tomorrow night at that! Was cutting it pretty close!!! Anyways, thanks again for your input and I'll give an update if it works!!