You did not include the specific model of Newgear Wireless router. I can only assume, via 'http://netgear.com/products/details/MR814.php' that you have the 'Model MR814'.
The manual for the MR814 is here 'http://bredband.webtechnord.com/doc/guider/dlink/Netgear%20-%20MR814%20Manual%20v2%20(Eng).pdf'.
-----
Perform below in parallel to 'Chapter 2' of the above manual.
01. Connect the Netgear wireless modem to the cable / DSL modem (which is turned OFF).
02. Connect an Ethernet cable between the PowerBook and the Netgear wireless modem.
Yes - there is a reason for this madness.
Simply, you want to have your internet connection as quickly as possible; plus, you want to have a configuration just incase your wireless connection fails - yet a wired link will work.
03. Turn ON the DSL / cable modem, turn ON the Netgear wireless router [locate the small hole in the rear - for the 'reset' button. Use a paperclip to press the 'reset' button for 10 or more seconds.], and turn ON or reboot your PowerBook.
04. Go to 'System Preferences' 'Network', and select 'Built-In Ethernet' from the 'Show:' popup menu.
If not already displayed, select 'Using DHCP' from the 'Configure IPv4:' popup menu.
You may / may not have to click on the 'Apply Now' button.
At this point IP numbers ['xxx.xxx.xxx.xxx' where each 'xxx' is between 0 and 255] should appear to the right of 'IP Address:', ' Subnet Mask:', and 'Router:'.
Typically, you would see something like '192.168.xxx.xxx' for the 'IP Address', '255.255.255.0' for the Subnet Mask', and '192.168.xxx.xxx' for the 'Router'.
You should now be able to surf the internet. This confirms your account, the router, and router to PowerBook connections.
If not, you may have to access the Netgear gear router for some manual settings. Such would be beyond the scope of this reply.
You can now remove the Ethernet cable and connect to the Netgear wireless modem via your 'System Preferernces' 'Network' 'Airport' options.
Now, follow the instructions of Chapter 3, of the above manual.
Only after you can connect (to the internet) wirelessly, should you consider any security related settings (via the Netgear wireless router's built-in web pages).
-----
Use 'Acrobat Reader' or 'Preview' to view the manual. Thus, you can search for 'reset', etc.
-----