How can I fix my PC when Windows 10 won’t boot?

John ran a tune-up utility and now his Windows 10 laptop won't start. What can he do?

I recently ran a free trial of a PC tune-up utility, including a disk clean-up routine, on my Windows 10 laptop. When it restarted, it reported a missing component. Said machine then bricked: boot begins, then the screen blanks.

Are there any steps that I can take to recover access to the machine? Failing that, can I recover my files from the hard drive, installed in a USB cradle? John

Microsoft has spent a lot of time (and money) trying to make Windows self-repairing, partly because it generally gets the blame when other programs - or users - try to "improve" it. Given that tens of thousands of expert programmers have worked on the code over the past 30 years, the number of safe, simple, significant and forwards-/backwards-compatible improvements may be quite small.