Well... different distros put things different places - which is confusing.
I am not familiar with Mandrake at all, and only marginally familiar with FC. I typically use Suse, but with regards to Samba, they should be pretty much the same. I assume Samba 3.x here.
You won't be able to magically login to samba with root unless you've added the "root" user to samba -
then set the password.
Keep in mind that samba does not set the security on the shares, which sounds like it could be your problem. Make sure the shares are owned by the user you expect to use them, or have a group assignment for multiples - chown and chmod for setting the proper access to the file system.
You might try looking at the Samba 3 By Example book over on www.samba.org
- which steps through configuration of Samba 3.
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