Here is a windows95 version Attax. It can help you beating the computer in Microscope Puzzle.
http://www.pressibus.org/ataxx/win/gbrondao.html

I played T7G when it first came out. Then about 10 years later, I played it again. Then my hard drive crashed and I never reinstalled T7G again after that.

I've never proceeded past this microscope puzzle. I always refused to skip it, yet I could never win. But I don't know what equals a "mistake," and/or what does not.

Here is one thing I don't understand: why can no one write a comprehensive, easy-to-understand, step-by-step guide that is guaranteed to beat this puzzle if the user follows it? (i.e. there are plenty of guides like that for the maze puzzle).

I'm going to presume that the non-existence of any such guide is due to the fact that the puzzle is impossible to solve other than by sheer, blind & miraculous (all three at once) luck.

I disagree. That's not the problem. This puzzle was still equally impossible or near-impossible in 1993 with computers from around 1993. The devs clearly messed up the design on this one and probably never play-tested it either. I assume that you visited the library about this puzzle three times and then chose the option to have the game automatically solve (a.k.a. skip) it.

It is simply not possible to write such a guide. As it is impossible to write a step-by-step guide how to beat chess, go or checkers. The number of possible moves simply explodes after just a few steps, making it impossible to simply write all the possibilities down.

It is not based on luck, however. There are clear strategies and tactics for winning the game and there are clear good moves and bad moves (although sometimes they turn out to be bad at first and very good later and vice versa). But it is still quite hard to articulate these strategies in words because they are based on thinking several steps ahead which is hard and takes a LOT of concentration if you do it all in your head.

I practiced a bit and eventually managed to wrap my head around this game and can now beat the AI after a few tries, but I could not really explain in words how to do it.

If you don't want to invest the time, simply use this program, it will tell you exactly which moves to use to beat the game AI:
http://analogbit.com/software/infection_ai/

I'm not sure "investing time" is necessarily a viable option. I've spent dozens and dozens of hours on this puzzle in my previous attempts. Perhaps investing time would only help in cases for someone who understands why he/she is winning or losing. But for someone who does not understand, then more time played might not result in better understanding/less losing.

Thanks though. I appreciate the link and your feedback. I'll probably use that link if I ever install T7G again, or else I'll just skip the puzzle via the library. Wouldn't the library skip option be even better than using the link though, since the library option is simpler and the effect on the game is identical to the link option?

Does Stauf say anything unique when you beat him on this puzzle?

That would be worth using the link for...

....unless....

... I've watched a video of this puzzle on youtube where Stauf is talking in a a super-sped-up Alvin the chipmunk type voice. That is certainly not how he is supposed to sound. Does the GOG version wreck his voice on this puzzle?

Well, basically you lose because you fail to capture more pieces than the AI. But thinking far enough ahead on how to simultaneously both protect as many of your own pieces and capture as many of the AI pieces as possible is just really hard for humans in general. Even the author of the linked Javascript AI does not like the game. He writes: source: http://analogbit.com/2015/02/24/beating-the-7th-guest-infection-ai/

As far as I know there is NO penalty or consequence for using the library book. The developers wrote in the instructions that there WOULD be consequences, but as far as I know they didn't actually program any in.

There is no message or video on immediately solving this puzzle, but IIRC it unlocks a drama mask/video in the same room (Dutton & Temple) which you will be able to see even after using the library book.

ScummVM has an option to play certain videos double speed (mainly the walk and turn animations). Maybe early ScummVM versions accidentally sped up additional videos? As far as I know this does not happen in current versions of ScummVM and almost everything plays at the speed it should.

Thanks Lafazar. Your post is world-class information.

In addition to the misleading information when the player character says "I'll have to start again" even when he doesn't necessarily, I have noticed other misleading information in this puzzle too. If you do a move that converts the maximum number of enemy molecules, then Stauf shouts "Curses!". This implies that the player is winning and has just acquired a huge advantage over Stauf. However, in actual fact, those moves usually mean nothing at all, because Stauf can easily reverse their damage and make them as irrelevant as if they never happened.

Just an FYI for everybody banging their heads over it, the things the characters say throughout the microscope game aren't random or glitches: each line is prompted by a specific number of pieces getting taken by one player or the other on a single move. If the player takes 4 of Stauf's pieces, he'll yell "Curses!" If you take five, the player will say "Great move!," if you take six you'll say "Yes!," and if seven you'll say "There!" The "I'm going to have to start again" line gets said if the computer takes five of your pieces--if it takes six your character will say "Should I have done that?," and if it takes seven he'll say "I have a bad feeling about this..." So don't take anything they say as a clue about your progress--it's just reacting to what happened on that specific turn. Hope that helps a little.