<<<...when I opened Outlook Express a dial up prompt box appeared and failed to connect me...>>>
Go to "Control Panel > Internet Options", select the Connections tab and ensure you have selected "Never dial a connection".
You will almost certainly need to uninstall the software used for your USB modem to avoid conflicts with your connection via the router.
Not sure why your USB Wireless Adapter is crashing the PC but, if you have USB 1.1 ports as well as the USB 2.0 card, try those instead. The 12Mbps speed of USB 1.1 is adequate for internet connections.