Confusing hardware setup

[Crazy_Frog1]

I recently purchased this PC but, the hard drive setup doesn't make sense to me. They installed the OS on a 1TB HDD and used the 500GB SSD stick that's plugged into the motherboard as the storage drive. I think it should be the other way around.

I have 2 SSD's from my previous PC that I can use. One is 500GB and the other is 1TB. What I want to do is, clone the current storage drive data onto my 1TB SSD and repurpose the 500GB SSD stick as the primary OS drive by cloning the OS from the 1TB HDD onto it. From past experience of doing something similar (upgrading an HDD storage drive to an SSD storage drive), the cloning process will assign a new letter to the drive (in my case it was E).
My question is, how do I change it back to C: so it boots from there?

[TheOldMan]

What I have learned about these things - Windows will cause you problems when it sees the new drive and reassign drive letters.  If the existing 1TB drive is the boot drive and it assigned already C:, then clone the drive outside of Windows.  In other words use either Acronis in it's own environment, use clonezilla and boot to the clonezilla disc, whatever cloning software you like that can boot in its own environment, or a Linux disro that can clone.  Do not do the cloning inside of Windows and do not let Windows see the new clone.  Remove all drives and only have the old host drive and the new host drive in the system.  Do the cloning and shut down.  Remove the old host drive and then put the new C: drive in SATA 0 position, with no other drive installed.  Boot the system to the new clone, to make sure it will boot and make sure all things work properly.

Then you can add any other drive in addition for whatever purpose you desire.

[itsmyname]

@Crazy_Frog1 --

They installed the OS on a 1TB HDD and used the 500GB SSD stick that's plugged into the motherboard as the storage drive. I think it should be the other way around.

Agreed.

> I have 2 SSD's from my previous PC that I can use. One is 500GB 

Great!

I agree with @TheOldMan  --

1. Download and install some "disk-cloning" software, such as "Macrium Reflect".
2. Use that software to create something bootable, either on DVD-writable media, or onto a USB memory-stick.
3. Shutdown.
4. Disconnect the data/power from the 1TB disk-drive.
5. Connect the data/power to your "spare" 500 GB disk-drivwe.
6. Boot from that new media, and "clone" from the internal memory-stick onto your "spare" 500 GB disk.
7. Shutdown.
8. Disconnect and remove the "spare".
9. Reconnect the 1TB disk-drive.
10. Boot again from the new media, and "clone" from the  new 1TB disk-drive onto the internal memory-stick.  
11. Shutdown.
12. Disconnect the power & data cables from the new 1TB disk-drive.
13. Power-on the computer, and enter BIOS SETUP. Check that the first bootable device is the new internal memory-stick. Save/Exit from BIOS SETUP.
14. Boot Windows from the internal memory-stick, to confirm that the cloning worked correctly. Sometimes, with Macrium Reflect, the first boot does not complete. In that case, power-off, by disconnecting the AC power cord. Reconnect the cord, power-on, and reboot into Windows. That works for me.
15. Shutdown.
16. Reconnect the data/power cables to the 1TB disk-drive.
17. Boot your computer from the Macrium-created media. Select that 1TB disk-drive, and "wipe/initialize" it, to make it an "empty" volume.
18. Shutdown.
19. Boot Windows from the internal memory-stick, and check that the 1TB is both "accessible" and "empty". It probably will be the "D:" or "E:" drive-letter, and your CD/DVD will probably be "E:" or "D:". You may need to "manage" Windows, to assign a drive-letter to the "empty" disk-drive.
20. Copy your personal files from your "old" 500 GB SSD onto the new 1TB disk-drive.

Done.