Here’s a workaround for a weird problem with Windows XP and Samba.
If you keep getting ‘access denied’ messages on your Samba shares, try to switch off the password encryption. It is a very unsafe workaround, but it did help in my case:
You can turn encrytion off in XP, by going to Administrative Tolls -> Local Policies -> Security Options, and enabling Microsoft Network Client: send unencrypted passwords to third-party SMB services