How to Port Forward on my dlink DIR-628 router?

Port forwarding essentially works the same on all consumer routers -- you login to your router's "control panel" (usually its default address is something like http://192.168.1.1) and then you get into the port forwarding (sometimes it can be called Port Triggering, which is similar). You specify the port that you want to capture from your WAN address and specify the IP (and port) on your internal LAN that you want it to redirect to.

So in your case, you would want to port forward port 25565 on your WAN interface to <LAN IP address of your Minecraft server> on port 25565.

Note: Usually you want your LAN IP for a server to be static (vs. DHCP). If you use DHCP, make sure you have a DHCP reservation setup so your server gets the same address (otherwise the port forwarding will end up at whatever machine gets the address you configured the forwarding for)

Also, do you have a separate modem or is it built into your router? If the modem is separate from your router, you essentially need to port forward twice -- once from your WAN interface to your router and once from your router to your LAN Server IP Address. In this configuration, I typically configure the modem to DMZ everything to my router (all traffic is redirected to the router) and then I just have to setup one port forwarding rule in the router (Make sure your router has the necessary firewall/NAT settings enabled if you take that approach)

By default, Windows firewall will still be blocking that port. You have to open that port on the MC server's firewall as well…

http://portforward.com/english/routers/port_forwarding/Dlink/DIR-628/Minecraft_Server.htm

Also make sure firewalls on the computer don't get in the way. You can turn them off temporarily as a test.