Setup Airport Extreme on PC

I'm trying to get my PC to recognize my Airport Extreme. I connected the AirPort Extreme directly to the cable modem and the Airport utility software is up to date. I open Airport Utility and it can't discover the AirPort Extreme base station. It says "Airport Utility was unable to find any AirPort base stations. Please make sure the AirPort base station you want to set up is plugged in and in range of your computer, and then click rescan to try again." I've made sure that everything is plugged in correctly. The ethernet cord isn't broken as it is plugged in to my PC right now to access the internet. What am I doing wrong? I thought that maybe my PC isn't capable of receiving a wireless signal since its around three years old (Dell Dimension 4600). How do I make sure that my PC is capable of receiving wireless signal? If it isn't then do I just have to purchase a wireless card and install it? Any help is appreciated!

OK I went out and bought an ethernet cord and connected it directly from the AirPort Extreme to my PC. I still can't connect to the internet though. Its asking for IP addresses and all these other things. Honestly, I'm a wireless n00b so could someone please help me out?

I got it to work a little bit earlier today but it was sooo slow. I went back to try and fix it and now I'm in worse shape than I was before. Now when I try and setup my AirPort Extreme in AirPort Utility it give me error 6753 "An error occurred while trying to access the base station. Make sure your network connection is valid and try again." Again, I'm connecting the AirPort Extreme to my PC with an ethernet cord. Anyone have any clue on whats going on? I'm really desperate here.