Alpha Version 0.815 included E1M5 and improved lighting in most levels and more easter eggs
and few little fixes e.g correct amount of monsters in E1M3
Alpha Version 0.815 was rehosted on Doom Italia Doomitalia.it
Bug with installers:
If you get a error saying corrupted file.
Clear you temp files
Make sure Show hidden files is on.
Click organize in any folder, And click Folder and search options, Click View tab, Under Hidden file and folders, Click "show hidden files" Then go to "C:\Users\(what ever user you are\AppData\Local\Temp"
Go into the temp folder and delete everything. If you try and delete the folder it'll delete nothing. Anything in another folder in the temp folder you'll need to go into it as well because it'll also delete nothing otherwise.
You will find that not everything can be deleted in the end. You should end up with only 1 or 2 files depending on what all you have running.After deleting your temporary files try the install again. It should work now. This error should only happen if you install a version one after another