Blue screen: can't open Windows 10

I have an ex-corporate Lenovo laptop given to me when the project ended. All worked fine for 3 years on a Spectrum router in old apartment. I moved. I used my T-Mobile Android phone as a hotspot in my new apartment. All worked fine. Then I purchased a T-Mobile router and set it up. It buffered a bit, called T-Mobile and got everything sorted. 7 days later I woke up to a blue screen telling me I can't access Windows 10 This is NOT the BSOD! It gives me diagnostics but I tried every one and nothing works. I have access to Command Prompt and it immediately takes me to X:\windows\system32 I switch

Question by Elephant 2 on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.