>>>>>and others are effectively duplicates e.g. "A" and "a" are the same because Windows file names aren't case sensitive.
>>>>>A better estimate is 10 digits 0-9 + 26 alphabetic chars, or 36 total chars.
>>>
>>>You're right! 60 million it is, then.
>>
>>Add a few more characters to the base, which are allowed in Windows - parentheses, space, underscore, ampersand, perhaps brackets and braces... it grows.
>
>For me the "probably no trouble in other systems" rule only adds underscore to those 36 chars.

I would have said the same, if there wasn't the word "Windows" on the line above. But then that line may not come from the starter of this thread.

I actually wouldn't say the same anyway, I'd have said "rule adds only underscore to those 36 chars". But then most of the natives make the same mistake daily... or else YOLO wouldn't become a famous acronym.