I think I see what's happening. I know I wrote a lot the last time and I think you missed one key point. You need to open a command prompt then type ipconfig /all. Click Start, Click RUN, then type CMD and press enter (I may have left off pressing enter). Then type IPCONFIG /ALL.
What your looking for is if your WiFi has an IP Address. If it does, then follow the previous post.
I guess I need to ask "Why" you have a Linksys WPC54G (PCMCIA card) if you don't have a WiFi router. Do you have a WiFi router? Is it in use for something? Do you have other wireless computers which you need to share files/printers with?
Understand my confusion. Usually the only reason for someone to buy a pcmcia wireless card is because they are going to connect to a wifi router. Since you can't get broadband (dsl/cable/fios,etc.), I don't see why you have the pcmcia card, unless you use it at hotspots like internet cafe's, bookstores, coffee shops, etc. Please help me understand some more.
If you have a wifi router or not, you'll need to manually configure the laptop's network WPC54G network settings. If you have the router, that's where the DHCP (automatic network settings) come from. If not, you'll need to manually set them, or you'll keep getting random settings which will cause your wii to lose connection. I don't think the Wii Wireless adapter for a PC will resolve that.
So, do you have a wifi router? Do that ipconfig /all command and copy the info here so I can see which type of address you have. Look for the line DHCP ENABLED, I'm interested if it's YES or NO. The IP address numbers will tell me what kind of issues you might have.