Oh, I see! You actually installed it there. Gotcha!
Well, everything in the folder looks 100%. The file sizes are correct, the amount of files there are...
I don't know specifically why the Otome Dream error is popping up... But it looks like it can't read the original "nss.npa" file...
I have a nagging feeling in the back of my head that the files that were installed, even if they LOOK correct, might not be. Like they're full of garbage data.
Pop into the DX folder, and look for the file named: "dmrop.ngs" Right-click on it, and select "Open with..." Select the "More apps v" text, then scroll down to find "Windows Media Player". Let it open. It will complain that it doesn't recognize the extension, but try to play it anyways by clicking on "Yes".
Let me know if that plays properly.
I know someone once downloaded the ISO from the internet, but their ISP was flakey. Even though the ISO seemed to work, the data that was extracted somehow ended up corrupt. They had to redownload the ISO, and then used a different ISO mounting program, Virtual CloneDrive.
Somehow that managed to let it work. But I honestly am not sure about your issue.
Got any anti-virus programs that might be blocking programs?