It would be faster, easier, and lower-risk to specify the custom partition sizes as part of the clone operation itself rather than doing it afterward with another tool. The "Cloning a disk" page from the Reflect online user manual explains how to do that -- direct link here
, and look at Steps 4 and 5. In terms of making the new clone target bootable and retiring the old one, I would suggest the following:
- Create Rescue Media and make sure you can boot your system from it just in case. Do NOT simply rely on the boot menu recovery option for this. Make actual "external" Rescue Media on a flash drive or CD/DVD.
- Perform the clone.
- Shut down your system and temporarily disconnect the clone source drive (your 450GB drive). Then connect your clone target (the 480GB SSD) via internal SATA if you haven't already done that. If you had that SSD connected via SATA to USB adapter, for example, you won't be able to boot from it like that.
- Try booting your system. In many cases Windows will start right up from the clone target. If that doesn't happen, boot your PC from your external Rescue Media and run Fix Boot Problems, then try again. Either way, the new SSD will become your C drive automatically because Windows always assigns C to the partition it booted from.
- Once you have your system booting from the new SSD, you can reconnect your old SSD. Boot your system again and make sure you still booted from the new SSD
by checking the size of your C drive. If so, then if you want to completely repurpose the old SSD, I would use diskpart's "clean" command to completely wipe the disk, including all hidden partitions, and then you can repartition it however you want.
- In terms of the "dual boot Win10/Reflect", it sounds like you're referring to the boot menu recovery option. That should still be working at this point, but if not, open Reflect, go to the Create Rescue Media wizard, and recreate it