OK, at least we now have a reasonably clear idea of the problem, so let me obtain a bit more info from you...
1. As your system stands now, your 1 TB Seagate is your boot drive (and the OS is ?).
2. The system boots just fine and functions without any problems, right?
3. When you install the Samsung 250 GB SSD in your system you've ENSURED that the drive is securely connected to an appropriate SATA data connector on the motherboard, right?
4. And ditto for connecting the SSD to a power connector of your PSU, right?
5. So now when you boot to the OS with both drives connected, the Samsung is performing as a SECONDARY drive in the system, right?
6. And you've checked Device Manager to determine that the SSD is listed under "Disk drives"?
7. And assuming it is, you've checked Disk Management to determine the SSD is listed there?
8. We'll assume the SSD is non-defective. If you have any qualms about that, check out the disk with the Samsung Magician program, OK?
9. What is the TOTAL data contained on your 1 TB boot drive?
10. Can I assume that drive has a single C: partition or is it multi-partitioned?
11. If multi-partitioned, what is the size of the C: partition and provide the total data contents in that partition.
Please answer my questions clearly and then we'll go on from there, OK?