Windows – i have not access to shared files in a network… needs a permission

Try this on the Windows 7 machine:

1. Open Administrative Tools -> Local Security Policy.
2. Click on Local Policies -> User Rights Assignment on the left.
3. Double-click "Deny access to this computer from network".
4. Select Guest and click Remove.
5. click OK.
6. EDIT: Ensure in the Permissions for the network share, that Guest is included, since it's no longer part of the Everyone group.
7. Use regedit to go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System and create or modify the value of LocalAccountTokenFilterPolicy (32-bit dword) to 1, so the remote logon token will not be filtered (see here).

Try mapping it as a network drive and providing a different user name in step 6. If that doesn't work try the Net Use command to change the credentials used when accessing the machine. Windows will only allow you to connect to a machine using one set of credentials, so sometimes it trys to connect to say a printer first with the guest account, and that is why you can't access the shared folder using different credentials. "net use * /delete" will clear any existing connections.

Also I have had strange problems before where I was only able to use the Administrator account to connect, but that was probably because I was using hidden administrative shares