"anyways, i've already requested my isp to change my router settings to a modem type. i guess this eliminates the port forwarding matter. i'll try later tonight what happens."
I do not understand this request. Can your ISP change your router settings??!!
After having read the manual and this thread over again, i would do the following:
1. fully reset the zyxel modem/router to the factory defaults (make sure you've a backup of the data provided by your ISP like pwd, primary and secondary DNS, protocol type in case this is not managed automatically with booting up the router
2. After the reboot check that you've connectivity to the Internet.
3. Keep DHCP for assigning the IP adresses of your machine(s) DHCP=Server Chapter 3.8
4. Choose SUA chapter 3.14
5. Chapter 3.15 is the portforwarding stuff: find the ip of the PC running HFS, if you have only one machine connected it should be 192.168.1.33 assigned by DHCP of your router.
The list of page 3-19 should read:
Menu 15 - SUA Server Setup
Port# IP Address
80 192.168.1.33
(you now have forwarded port 80 from the WAN side of your router to port 80 of the PC with ip 192.168.1.33, where HFS should listen and serve the requests)
6. Run HFS on port 80
8. Change any settings in the router back to your needs.
If this does not work, check/update the firmware of your router.