sorry for necropost.i have the same issue and could not find any solution. perhaps someone has figured it out after 5 years?
https://www.reddit.com/r/osugame/comments/ivsct2/til_i_learned_that_osz_osu_beatmap_files_are_just/i
do not have any file associations set up in regards to osu files.
poc:
1. i download a .zip file
2. it opens my osu automatically (i have auto open in browser disabled)
3. osu! tries to process the .zip file as a beatmap file (?)
4. the .zip file is deleted.
troubleshooting:
# Find file type associations
- assoc | findstr /i "osu"
- i set all associations to nothing (NULL)
- i used FileTypesMan to delete all osu file extensions as well as their associations
i rebooted after removing everything osu file-type related.
nothing has worked.
the .zip file is set to WinRAR.
solution:
(temporary and dumb): - rename the osu executable.
warning: this will throw a System.Exception: Executable filename is not correct!.
but at least you can download .zip files again.