BSOD followed by disk read error and driver letter change

Recently I started getting two different BSOD errors which I thought I had fixed the problem for but they started happening again and on this occasion I've ended up with a disk read error. What I have discovered is that somehow my c drive has become my d drive. I've tried to change it using diskpart but when I restart the computer I figure out the the changes have reverted. I've done a dskchk which did some repairs but the windowns recovery environment still can't find the operating system (as it is still on the other drive I imagine. Can anyone help? Thanks in advance

Welcome to the forum.

Be aware that the drive letters shown in the recovery environment will not necessarily correspond to those used by Windows. When it starts it arbitrarily assigns drive letters for it's own use. It may show the Windows drive as D: but that is of no relevance outside the recovery environment

Well bootrec doesn't work, I get element not found errors. I've run out of ideas

I ran startup repair overnight and in the morning it was fixed.