How can I remove old HDD, which has system partition on it?

Just to be sure I understand...

You can't boot with old HDD removed? Then system files weren't transferred correctly. Or that double active partition is a problem.

And you only have one system in boot menu? Just Windows 10? If so, removing old HDD and performing System repair is probably best option. But you can also do it your way (reversing actions.)

I would still use Macrium reflect to make image of system (Drive C: - where system is) and make bootable USB stick.

First: I just wanted thank you for your help, because you help me a lot.

I didn't try to boot after I marked the new System Reserved active, because I was afraid about not being able to boot, and I have a lot of schoolwork on the weekend ( mainly programming so I need my computer), but theoretically it must be able to boot from the old HDD, because this new SRP (which is still active) doesn't do anything while the old SRP's doing the boot, am I right?
But I think Recovery shouldn't be active, should it? Because I searched for Disk Management screenshots (I know it's not the best way) but it wasn't active on any of the pics.

Answers for your questions:
1. I did try it once, (before I marked it active) and it didn't boot from the Drive 0 only from the old HDD.
2. In boot menu there is win 10, 7, and older windows version (it is an XP, but I haven't used it for ages (actually it doesn't boot at all, because I just left it on the drive before I moved it to my new PC 2 years ago)) Win 7 is on the old HDD.

But what I'm thinking now is EasyBCD didn't make this partition active as it said it would, so I think maybe it didn't other automatic operations as it said and that causes my problems : "Upon selecting the “Change boot drive” you’ll be prompted to select which letter you’d like to use as the new boot partition. When you confirm the selection, EasyBCD will automatically:

• Install the BOOTMGR bootloader to the selected partition
• Make the selected partition active
• Install the bootloader to both the bootsector and the MBR of the selected partition
• Copy all entries from the old boot partition to the newly-selected one
• Update partition references to work with the new boot partition" It's from EasyBCD website

Critical points are marked in this tutorial (I gave you link, when I mentioned EasyBCD).

I asked about what is in your boot menu (and what is booting), because you have some kind of mess... Removing old HDD (keep it for booting from it in case anything goes wrong) and performing system repair will give you just Windows 10.

tutorials system-repair-disc-create-windows-10

Thank you, but I used that tutorial, and I followed every thing excluding I moved it to H (that's why it had a letter) instead of C.
Do you think I should make the Recovery inactive? Because it's usually inactive, for example in my dad's PC. And after that only the Reserved would be active, so everything "must" be ok.

it should be OK. (I would make that repair disk first..) :)

The strange thing is MiniToolPartition sees the Recovery P. as inactive while my DiskManger still sees as active.Should I trust MiniTool? And the thing is if only one active partition is possible then why didn't DiskManger warn me about it when I marked the System Reserved as Active?

Edit: and EaseUS doesn't see it active, as well. And EaseUs says in the status: the new SRP is simply active, but the old SRP is System. Doesn't the new SRP have to be System, as well?

Also edit: MiniTool sees it as a System Partition, so i think it should be okay. I will give it a try next morning.
One more edit: Now Disk Manager is not saying that the Recovery P is active.

AdamBlack said:

Thank you guys,

You really saved my ass The problem is solved, I learned so much, so hopefully I won't have any problems in the future with this procedure.

Thanks a million.

Great to see you solved it. There is a lot of great tools around, one has just to pick one and follow procedure.

I know I said this many times before, but... Once you have system set up as you wish, make a backup of it. Macrium reflect is such a great tool, it is unbelievable that it is free to use...