Hello, I seem to be having a bit of trouble forwarding my ports. These are the exact words from www.portforward.com: "The F5D8233-4 will not allow you to forward enough ports, to run Blockland. You should try using the DMZ portion of this router if it is available." Can anyone help me with what to enter in the DMZ portion, and if this will expose me to hackers? (It says that IP entered will be excluded from all firewalls.)
Yeh I have seen this problem before, some routers apparently don't support Port Forwarding, and portforward.com comes up with that lovely message.
Just a quick DMZ explaination:

Basically it opens up the DMZ to anything in the internet (opens all ports, disables firewall etc), and the normal LAN is unnaffected and has no direct link to the internet or the DMZ, thus being protected. Some routers can emulate this with only one router in use, and what this does is basically disable all protection which the router has inbuilt for the IP address you enter.
Most ISPs have a certain amount of protection at their end, and then it gets to your routers protection, and then finally to your computer and its protection. To be honest, setting something as a V-DMZ shouldnt be a problem, as long as you are not stupid in what you do (as Bisjac said) and you have decent protection on your computer (AVG, Spybot-S&D, Comodo ... Etc.)
If you are concerned I say that google is your friend, and anything you are uncertain about ask people around here, they are generally quite nice and most will help you out, if they can, if you act appropriately and not idiotically.