Help! What does this error message mean and how can I fix it?

[Hypotenuse]

Recently my computer has been refusing to run Lemmini and SuperLemmini, it gives me the following error message:

CRC error for file C:\Users\PC\Downloads\lemmingswin\SOUND\BANG.WAV. (CRC is 0x550565b2, expected 0x54056532.)

I'm guessing that means there is something going on with the sound file, but I don't know what to do about it. (The sound file plays just fine by itself if I run it in media player.) Should I redownload Win95 lemmings?

[Flopsy]

Are you running the latest version of Super Lemmini which is 0.102b?

I had this problem prior to this version coming out but after I upgraded to 0.102b the extraction process completed just fine.

This is a common error message and it meant I wasn't able to play Super Lemmini for a while but I never had this problem with standard Lemmini.

[Simon]

What does it mean: The file doesn't contain exactly what SL believes it should contain. CRC is a hashing function. Given equal input files, CRC outputs the same hex string. Two files with different CRC are guaranteed to be different. Two files with equal CRC are probably equal.

Why is the file different: Lemmini loves to eat or mutilate your files, then complain they're different. We've criticized that. Allegedly, SL has improved on Lemmini's voracity. Maybe SL is still not perfect at leaving data alone, or maybe your disk has bit rot.

What you should do: Hunt for a copy of whatever SL expects, and replace your file with that. Keep SL up to date.

-- Simon

[Tsyu]

That "wrong" CRC is that of SuperLemmini's bang.wav. What most likely happened here is you once tried to extract Windows Lemmings to its own folder, resulting in some of the files being overwritten. You're supposed to extract to a different folder.

You'll have to get a fresh copy of Windows Lemmings and extract from that.

SuperLemmini 0.103 will include a safeguard to prevent the user from making this error.

[ccexplore]

To be honest, I'm not really sure why a CRC check is warranted for something so non-essential as a sound file.  Seems like a non-blocking warning would be better so user at least have the option to continue with the game.  It is of note that Hypotenuse says the WAV file plays fine so it isn't even actually corrupted it seems.  Honestly, I'm not sure I buy Tsyu's theory on what's happening.

[Tsyu]

Hypotenuse's bang.wav isn't corrupted; it's SuperLemmini's patched version, but it somehow replaced Windows Lemmings' version, likely due to the incorrect installation procedure that I described in my last post. (If you're wondering why SuperLemmini would patch a simple sound file, it's to remove a click at the end.)

[namida]

Protecting against overwriting the source files does seem like a very good idea.

In fact, I would suggest take this one step further: Don't ask for an arbitrary target directory, just extract to subfolders of wherever SuperLemmini.jar is stored.

And, if you do patch any files, accept the post-patch copies of them as well as the pre-patch ones.

[Hypotenuse]

Ok yep, spot on. I just redownloaded Win95 lemmings and went through the extraction again. Lemmini up and running! Thanks a bunch folks! And by the way, that user error prevention thing sounds like a good addition for SuperLemmini
Note: accidentally posted this in my old "help I'm technologically challenged" thread, please ignore that one lol