https://www.google.com/search?q=8000FFFF finds a wealth of priors but if I were mine I'd read a few "solved" ones and see if they help.

That said I have run into folk that run W7 on unsupported hardware such as a Skylake or newer CPU and failures happen. There is no support for that system so you have to tread carefully as the owner may explode over the passing of support on that. That is, they know the fix but are upset about it.

I've seen other causes such as the need to clean up disk space, run CHKDSK /F/R/X and go deep with malware scans but this one is trouble as no single cause or cure.

What to do? Work the easy ones like disk cleanup and chkdsk then do the malware scans. If your PC is on Skylake CPUs or later, I'd move to W10 as it's still free to upgrade.