Permissions on shared folders and LACK OF thumbnail function

I'm having trouble with the thumbnail function. If I make the
permissions on my shared folders to read-only, in order to avoid
people deleting a movie after watching it.....then MCE is no longer
able to remember the thumbnails it makes of all the videos.
(of course because the file ethumbs.db is now read-only)

This problem has been at me for some time. I think MCE would be great
if it got rid of this "delete" problem. I don't want my kids (or my
wife) accidently deleting a movie.

A quick summary of my system:
2 computers (1xWindows2000 and 1xWindowsXP Pro) that act as servers.
- contains shares for music, photos and videos.
2 computers both running Windows MCE 2005 that are connected to
televisions.

The computers running MCE the users are automatically logged in as a
specific group that has read-only privaleges on the computers that
contain the media on the network.
This is fine to prevent deletion BUT! now when MCE generates the
thumbnails....
It cant write them to the ethumbs.db file! So it can't recall the
thumbnails. It has to generate them each time.

I've tried setting the permissions for this particular file in the
security tab to full-access but since the share is listed as
read-only....it's read-only!

Can anyone help.

(sorry for the long windedness of this post)

Sincerely,
Noah