Resident Evil 1.5, for those unaware, was the game that Resident Evil 2 almost was. Capcom was unhappy with the game as it neared its release date and decided to scrap the project and start all over again instead of releasing what they had. That scrapped build has become known as "Resident Evil 1.5," and it's been in the hands of fans who have been restoring the project in private.
The team has had continued problems with someone named "Colvin" trying to sell playable builds to others and just otherwise being a nuisance and risking the project's security. So the team has decided to release what they have, an "unstable mess," as they call it, to everyone. This is the first time that a playable build of Resident Evil 1.5 has been released to the public. Download the unfinished ISO from here.