PC not booting after clone attempt

I suspect you have got caught in a Windows safety feature. You have not told us details of prior history, so I'm not sure.

Windows has a feature designed to help out automatically in future if ever some of the system files are corrupted. At the time when Windows first is installed, the installation routine examines the entire system for a second storage device. If it finds one, this is what it does. It WILL install Windows and all its files on the specified boot drive. BUT it also will place copies of important system files in a semi-hidden Partition you cannot "see" normally on the second storage device. The idea is that, if ever the boot drive's files are corrupted, the boot sequence will go to the other drive and find the backups, copy over a good copy of the corrupted file(s), then complete the boot. Self-fixing for your problem! Handy! From then on, at EVERY boot-up it will look for that second device to verify the extra copies are there safely and, if they are NOT found, it will refuse to boot!

On the other hand, this system can be partly re-routed. IF you have only ONE storage device in your machine at the time Windows is installed, the backup copies will be placed instead on the only drive in the system - the same drive Windows is being installed on. Then it CAN boot from that drive only.

Now, you cloned from one SSD to another using a third-party software tool. My guess is that it did NOT clone from old to new ALL of the Partitions on the old SSD - in particular, the "hidden" Partition with the backups. So if you try to boot with ONLY the NEW SSD in place it can't find the backups and fails, telling you it cannot find the OS. But if you also install the old SSD, the backups are found on it and things work.

There is a fix for this that certainly works when you have conventional HDD's, so I assume it will work for you, too. To do this you need a Windows Install CD for the SAME version of Windows you are using, even if it is not the exact CD used originally to Install your Windows. You need to set up your system so that only the NEW SSD with the clone copy on it is present. Then you need to set your BIOS Boot Priority so it will boot and run from the Install CD (or other storage device). When you do boot it will start up the Install process. Do NOT run a normal Install!! Search instead for a Repair Install and run that. This will search the only storage device present (your new SSD) and find that the backups are missing. Then it will create a new hidden Partition and place the backups in it. When the process completes, shut down and remove the Install CD. Reboot into BIOS Setup to re-adjust your Boot Priority setting to what you want, then SAVE and EXIT. The machine should be able to boot cleanly with ONLY that new SSD installed.

When that works, you can just run that way or shut down and add anything else you like.