See also the FAQ:
FAQ: I cannot delete / deactivate my file.
Similar to deleting your own posts in the forum, this function is also deactivated for all users. We would like to use the WebDisk to create a permanent OMSI download archive, with as little data loss as possible. Old versions are not deleted either!
If you want to delete your entry, report the entry with the "Report" button and specify the reason for the deletion. A moderator will then mark the corresponding file as deleted. After a period of 30 days the entry will be permanently removed from the WebDisk. Of course we respect the copyrights and everybody has the right to have his entry deleted. However, please remember that it is not community-friendly behaviour to delete all files out of frustration, personal differences or as a result of a short-circuit reaction and to withdraw them from the availability of the community.