MySQL datadir dosn't work exactly (no replies)

Hello,

I want to store my database files on localnetwork another computer.
How can i do?

So I tried some methods but isn't work;

I changed the datadir=C:/Documents and Settings/All Users/Application Data/MySQL/MySQL Server 5.1/Data/ to Z:/mydatas

(z: is mapped another computer and full access)

When I restart the mysql server is say to me "Can't create test file"

What would be happen?

Thank you.