Hi Helepolis,
thank you for your reply. I tried extracting it with 7zip just now, and I got the same issue. It is saying that images (.png files) for stage 3 and 4 are corrupt, the other files are extracting perfectly. I also tried with my system set to Japanese locale, but to no avail. I think the source I got it from must have corrupt over time.
I' hoping someone will provide another download link for the file, since there is a run of it on YouTube and Nico, there must be a functioning copy. Thanks again for any help.