> My XP and Win 8.1 can recognize each other and share files, but my
> win10 does not give its files to XP or win 8.1.
I understood this from one website and I learned much about how to use the win10's security for the 1st time. it was about how to bring out "everyone" through "edit" - "add" - "advanced" - "find now"
now my win10 can share files with win8.
------
how to bring out xp's "everyone" as an user seems to be really tricky. I am working on it at the moment.
-------
for "everyone" as user
i need to make an entire V: as "read only security" except for V:\ABC whose security must be "deny all access".
for "admin" as user
i need to make the entire V: as "full control" including V:\ABC.
this part is easy, because it is the default.
when i selected V:\ABC to have "deny all access" all was greyed out already, so they couldnt be selected.