In the interests of posterity, and not because I always need to be right about everything, I just remoted into an XP Professional Service Pack 3 desktop, entered 53.2 megabytes of text, then successfully saved, reopened, edited, saved again, and reopened the document again using Notepad.
And, well, XP is oficially EOLed, but still out there in the wild. Anyway, hand-typing ~30 full pages of text is not very likely in either case ;)