Wi-Fi: How come I can only sometimes connect to the internet wirelessly but I can always connect via an ethernet?

I can always get online if I use the ethernet cable... Even when I can't get on http://google.com (or something) I can always get on 192.168.1.1 (the router admin page). This part is the key. This is not an issue with your wireless card, with the driver, or with interference. If you can always get to the router admin page over WiFi, then there is no hardware or air interface problem. The issue is likely with the network configuration. There may be a routing issue on your notebook which prevents it from communicating with the "wider world" correctly over the WiFi interface. It could also be an issue with the routers, although it seems unlikely that two different routers would be identically misconfigured. Since the issue is intermittent, I suspect that you may have multiple programs trying to manage the WiFi configuration in conflicting ways. I am guessing that you are using Windows XP, or upgraded from it, since your notebook came out in 2007? This was particularly an issue in Windows XP days, when notebook OEMs would bundle tray applets like "Realtek WiFi Config Manager" or "Dell Wireless Management Center" ... these were supposed to fix problems with Windows XP's standard Network Configuration for WiFi, but ended up creating more problems than they solved in every case I've ever seen. Without further about exactly what OS you're running and what software is managing the WiFi interface, I can't really give more details...