All my important data I keep a copy of on an external HD
Smart move. Sadly, reinstalling the operating system is ALWAYS a last resort option for so many reasons. Fortunately, you had some foresight with your data - you are not a normal user! But with a reinstall, all your programs, including your security defenses are gone. Plus you are set back months or even years in security updates.
You learn nothing that might help you prevent it from recurring. And BSODs are often caused by hardware or hardware drivers. Reinstalling Windows won't fix failing hardware and if the same drivers are used, may not fix a driver problem either. There's no assurance it won't BSOD again. So all that lost files and time reinstalling and all the time it takes to get Windows just the way you like it, is for naught.
As a rule, when format or reinstall are the among the first words out of someone's mouth, smile, say "thank you", and walk away. If other options are not explored first, find another "expert". As always, there is an exception to the rule where a format truly is the first option - those cases typically, though not always involve an in-law who "fixed" it.
By the way, have the dust bunnies and cobwebs been cleaned out of there in the last 6 months?