MSSQLSERVER service terminated unexpectedly - solution

Google groups wouldn't let me reply to any messages on this subject, so
I'm starting a new topic. I had this problem, and the error logs didn't
give anything useful. I thought I'd installed the latest service pack,
but since I'd done that I'd created a new instance and I didn't realise
I needed to patch that. Having done that these errors went away (MS
says they were fixed in SP3).

I hope this is helpful for anyone else Googling for this error message.