Win 7 32 bit inadvertendly changed primary disc drive letter from "C"

While working on an older custom built computer I attached a WD disc drive in an external enclosure via USB to see the files on the drive. It was a backup from another system that is using Windows 7 64Bit system. I checked the file then ejected the disc. Got a message that disc was in use. Went to "Computer" Closed the disc attempted to eject, ejected and removed. Observed my computer froze, was forced to shut down manually and when I restarted It would not boot. Went into system repair. System repair shows OS Window 7 on disc "D". System repair has been going for 14+ hours.

I have no idea how this occurred. I have been building Windows systems for 8+ years. never encountered this before. The importance of this system is that it is reserved for my annual tax filing and contains past tax files for several years. This data is backed up on DVDs so if I have to rebuild I can.
Thoughts and suggestions appreciated. Also If I am in the wrong area please forgive and direct to proper area. I do not use social media as a rule.

Welcome to the forum. Was the drive a clone of windows as it would have the same disk signature. If you attach the drive then try and boot will it boot then if so post screenshot from disk management showing all details of both disks

I build computers and as I am retired I mess with them often. The disc in the enclosure was a backup disc for another Windows 7 64 bit machine which I created a larger backup drive for. I did not label the replaced drive. so I fire up my TAXMAN Windows 7 32 bit machine and saw this enclosure on my desk, thought I can use this as a backup for TAXMAN. I plugged it into a front USB, simply looked at the files and then ejected it, unsuccessfully at first, which was the first weird thing. Finally got it to eject but then TAXMAN froze and I had to do a manual shutdown. when I rebooted system went to system repair which it has not completed after a day and a half. I shut the system down and using a DriveWire connected the TAXMan disc to a Win 10 machine and checked the files on disc. All of the files including the OS seem to be there, Just under "D' drive instead of "C'.
I have two options that I am aware of: 1. Let repair run until it quits or 2. install win 7 pro 32 bit on another HDD and copy files from the original TAXMAN disc to the new disc.

This is why I consulted the forum for ideas and help. To answer your question directly, the external enclosure disc was not a clone but a backup of another system. I have no idea how or why my problem occurred.

samuria said:

post screenshot from disk management showing all details of both disks

ditto that

check out bcdboot

BCDBoot Command-Line Options | Microsoft Docs

Sorry guys but a screen shot is not going to happen as I cannot boot into the system. Attempts to boot result in system repair opening. The only way I can see files on the TAXMAN is thru my drivewire.
I am checking out the response from johnhoh to try it out. I will let you know.

I think that your computer is trying to boot from the backup disk

During post launch the boot menu and choose you main disk, not the backup disk.

If it doesn't work, shut down and detach the backup disk from the MB.

Thanks to all of you for your help, thoughts and advice. My problem is solved. I installed a new HDD, installed Windows 7 Professional 32 Bit, updated, installed the required tax software for each year needed. Took the original TAXMAN drive and connected it to my Windows 10 professional 64 bit machine using my DriveWire device. Copied the needed files from TAXMAN disc to a 128GB USB. I then copied the saved tax files to the new TAXMAN. Problem solved. Not techie but I got the result I needed. Computer works, stress gone. Thanks to all who replied. I learned some new lessons, relieved stress and met new guys. Thanks again to all of you.