Question I can't start windows without a specific disk

Sep 8, 2022
I've had Windows installed on an NVME M. 2 128 gb ssd for almost two years now, I remember installing modified Windows 10 on it (the ReviOS 2004 S1.0). I installed Windows on M. 2 with other disks connected to the PC, my 160 gb HD on SATA 1 and another 750 gb on SATA 2... Over time, the 160 gb HD started to cause a problem because it already had the most worn out useful life, so today I went after another HD to replace it. I hadn't changed anything in the BIOS, like changing the boot disk, I just changed it and turned it on, I didn't think anything would go wrong because Windows was installed on M. 2 and I had already selected it as the boot system at the time I I installed Windows. After I tried to boot the system, a notification started to harass me "reboot and select proper boot device or insert boot media in selected boot device and press a key", regardless of whether I reset or modify the settings in my BIOS (motherboard MSI B350 Tomahawk) the problem continued, until I decided to reinstall the 160 HD... And it worked! Windows loaded directly without even me having entered to configure something in the BIOS, but the reason I want to change it is because it is stopping giving a signal, it only worked when I left it suspended by the power supply cable (don't even try to tell me that this sucks, I KNOW! But he only showed signs of life when he got like that!). After logging into Windows and going into disk management, I noticed that my 160 HD is Healthy (System, Active, Primary Partition), and my M. 2 that Windows is installed on is Healthy (Startup, paging, Crash Dump, Primary Partition). Is there any way I can change the "System" disk so that my PC is not dependent on this broken HD occupying one of my SATA roads? (I used Google translate, sorry if anything mentioned is incongruous)
The problem is the hard drive contains the bootloader (noted by the partition marked as "System"). Whenever you install Windows, it'll check if there's an existing bootloader. If there is, it'll just update that one.

If you don't mind reinstalling Windows, then just reinstall Windows with the other drives disconnected.

If you don't want to do that, there is a workaround:
  • Shrink the OS partition by about 500MB
  • Create a new NTFS partition
  • Assign a drive letter to it (I'll use S: as an example)
  • Open a command line as an administrator
  • Type in diskpart
  • Type in list partition and find the partition you just created
  • Type in select partition # where # is the newly created partition
  • Type in active
  • Type in detail partition and verify "Active: Yes" is showing in the listing
  • Type in exit
  • Type in bcdboot C:\Windows /s S: . Though make sure C:\Windows is the actual OS you wanted to boot into (it may be another drive letter)
  • If you want, you can unassign the S: drive letter.
The steps are similar to the ones described in