I did a simple config:

server {
listen 80;
server_name localhost;

root Y:/www.mydomain.nl;
index index.php index.html index.htm default.html default.htm;
location / {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header Host $host;
#proxy_pass http://127.0.0.1:8000;
expires 3s;
max_ranges 0;
}
# deny access to .htaccess files, if Apache's document root
# concurs with nginx's one
#
location ~ /\.ht {
return 404;
}
location ~ ^/(xampp|security|phpmyadmin|licenses|webalizer|server-status|server-info|cpanel|configuration.php) {
return 404;
}
}

And accessed http://localhost/Disclaimer.txt
which works perfectly, your config is not optimal but the share works as it suppose to.
so its definitely a config issue and not a share issue.

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nginx for Windows http://nginx-win.ecsds.eu/