File permissions help

Hi folks,

I have recently moved from a Novell file server to a Microsoft 2003 Server. However, i am having some very strange problems with my users when they create new subfolders and files.

I have created a folder called [Share], and given the [Everyone] group Modify permissions on the structure below it. The structure below this share has been copied over from my old Novell server and has around 22300 folders and 164000 files. The thing is, when a user creates a NEW folder or a file, they become the sole owner of that file or folder. This means i have to go in, take ownership of the object, then add [Everyone] to the list of users. What am i doing wrong here?