Laptop Wireless Connectivity Issues

I have a Dell laptop that is about 4 years old. I had a Belkin wireless router and a Belkin Wireless Card. I have been having issues getting and keeping an Internet connection through that router. So, I just purchased a NetGear router the other day. I am still using my Belkin wireless card since the laptop does not have a wireless card built into it. Anyway, I am still have the same issues. I have a strong cable Internet connection and the wireless connection looks strong too but when I try to get online, I cannot. I checked with Belkin, NetGear and my ISP and they all say that it could be the way that something is/was set up in the laptop. I cannot find out what that is. I am tired of unplugging the router several times in order for the computer to pick up/keep a connection. Any thoughts as to what this may be? I highly doubt it is something with both routers or something with the cable modem since I can wire it directly and get a connection. Any advice on what I can fix in the computer to make this work everytime?