The mac starts up fine and goes to the login screen. After I enter my password the losing bar circles once then freezes, followed a few seconds later by the cursor changing from normal to the frozen-working-stuff-out-wheel-of-many-colours. The mac then stays in this condition perpetually.
I will gladly accept suggestions as to a course of action.
2008 Late, MacBook pro 13, running High Sierra
For some reason (which I'll gladly accept an explanation for) I cannot use any commands on startup, such as recovery, safety, and NVRAM, as it simply doesn't load anything. (I have a feeling that's related to me forcefully boot-installing the MacBook to high Sierra (HS) a few years ago, because originally it's spec wasn't up-to-date-enough to support HS, but am open to other ideas for the cause of that.)
There is no vital data on the machine, as I am operating entirely from Google drive.
I have the spare (so-slow-it's-effectively-non-functional) original HDD from the Mac (which I removed during a recent SSD upgrade.)
due to my internet speed being quite slow, I'd much prefer not wiping the machine and starting afresh, if it can be avoided.