Accidentally installed Windows 10 over 2 hard drives. Can I transfer everything to one?

A few months ago I had to reinstall Windows 10 on my PC. Though I have two internal hard drives connected to it, I only use one of them, with the other one only meant as a backup. When I installed Windows, I'm pretty sure I choose to install only on my primary HDD.

Fast-forward to a couple of days ago, I tried to remove the secondary hard drive and found out that my PC would not boot without it. After reconnecting it and checking on Disk Management, it turns out that Windows put some of its installation files on the secondary hard drive as well: The Recovery partition and the EFI partition. I'm not sure how this happened.

Here's a screenshot of what the disks look like on Disk Management:

So, is it possible to move the Recovery and the EFI System partitions from Disk 1 to Disk 0 (the primary one) without having to reinstall Windows?

1 Answer

Thanks for posting this. I literally just experienced the same issue. I had a 2TB SATA drive in my machine that I was using for backups and it never had a system installed on it. I just purchased a larger NVME M.2 drive than my original OS drive and created a fresh Windows 10 install on it. Everything was running fine until I decided to restructure my backup drive and noticed that it had partitions on it that I didn't create. The Disk Management app wouldn't delete the system partition from this backup drive nor would the CMD prompt with DISKPART. I eventually decided to boot off of the Windows USB and clean format the drive with the CMD prompt in that state, which worked.. however then my system on the main OS drive wasn't recognizible. Somehow it had installed the boot info to my backup without asking or informing me, but installing the main system to my main OS drive. I was able to fix it by booting with my Windows USB repair drive and rebuilding the boot record in the CMD prompt. I followed the instructions on this page and it worked perfectly to solve the main issue:

Now my drive is again visible in the BIOS and boots without issue, however it's missing the extra partitions. Does anyone know if these are needed? Can my OS drive get away without a spleen? And is there any way to restore them without doing a full reinstall? I'm also not convinced that a reinstall wouldn't just produce the same results unless I removed all the other drives. Any insight would be greatly appreciated!