The install is easy enough but it sets up the Linksys connection manager by default. Sometimes Windoze Wireless Zero Config works better than the manufacturers driver. Other times, it's the other way around. Try both. Also, make sure you have the latest drivers and connection manager from Linksys. See:
Oh crap. Linksys has "new and improved" the downloads and support web pages. Now, I can't find anything unless I know what the card looks like. Brilliant thinking (again).
Well, think about it. You have two wireless cards operating in the same machine, trying to connect to the same access point. Perhaps they're interfering with each other?
You don't have to disable the card in the device manager in what I guess is your HP Pavilion laptop. There's a switch or button on the laptop somewhere that will do the trick. Or, you can right click on the Broadcom icon in the system tray and select "disable".
No (unless you have another wireless device installed).
That's your firewire port. Leave it alone just in case you find one of the mythical and non-existent firewire network adapters.
That's the wireless PCI card inside the laptop that should have been doing much better than 7Mbits/sec. Since the WPC54GS works well, and the Broacom MiniPIC doesn't seem to work very well, methinks you might have grounds for asking for a warranty replacment of the Broadcom card from HP.
Correct. It should not interfere with the wireless.
Not really. However, it's still not exactly good enough. The
17-19Mbits/sec download over the internet is probably the limit for your cable modem connection. I would run the IPerf tests I previous suggested to make sure that you're getting at least the 25Mbits/sec thruput you should see with a 54Mbit/sec association, or somewhat faster with the "turbot, super-G, or whatever" mode enabled in the router.