This means that you are running a 32-bit version of Windows, which only supports up to 3.5 GB of RAM. You'll need to install the 64-bit version. You can use the Product Key of the 32-bit version to install the 64-bit version.
I've merged both threads.
AGP is an old interface, which is not being sold anymore. It's all PCI-Express these days (not to be confused with PCI). I believe that HDMI graphics cards where released after AGP was discontinued, so you'll have to replace your motherboard with a recent one that...
The AGP interface is quite old, you won't find any new hardware for this interface (it's all PCI-Express these days). You might find a used one on eBay.
Does your ISP require a "computer name" or "host name" to be set? If so, please change the computer name in the router accordingly. Also have you made sure that the modem is connected to the WAN port on the router and the computer is connected to one of the LAN ports? I would also suggest...
Switches don't use IP addresses, as they operate on a different layer in networking. If you connect the router directly to the modem, does the connection work properly?