[NAME].Simpson It appears that the operating system is on the SSD. Disk Management Graphical View should also show an EFI System Partition and one or more Recovery Partitions. You should replace the M.2 SSD. If you do not want to reinstall all your applications you need to clone your current SSD. Like I mentioned previously, you need to use something like Macrium Reflect Free Edition to create images of all the partitions on the current SSD and save them to the HDD. Otherwise, you could start fresh and replace the SSD and reinstall Windows. 
I have two hard drives on my XPS 8930. The primary is a 256MB SSD and my other one is a 1TB HDD. 256GB PCIe x4 SSD + 1TB 7200RPM HDD I would like to replace my 1TB HDD with a 1TB SSD. Or should I upgrade my 256MB SSD with a 1TB SSD? There seem to be a lot of options. What's the best one? Please advise. Thanks.
XPS 8930, upgrading HDD to SSD, #2