So just messing around I've managed to create my own little home network. I've done things like this before, networking two computers to share an internet connection, but now I've run into an issue.
My internet host as I guess you would call it is in my office, wireless internet access. I have a 50ft ethernet cable running from it to my Entertainment center computer (hooked up to my tv & receiver for movies & music & such) - that works fine. I have internet on both computers. I installed another ethernet card on my Entertainment center computer in an attempt to run a cable from it to hook up to my laptop on an intermittant basis, but I cannot get this to work.
I've tried a regular ethernet cable and a crossover cable, both get the message (network cable is unplugged). I tried conneciton sharing, and bridging, but nothing seems to be working. I'm hoping that this is even possible... I'll try to outline my network as best I can for a clearer picture.

any thoughts, ideas are welcome. Might not even be possible but I take the attitude that with computers, there IS a way to do it.
oh all computers are running XP SP3 (had vista for a minute, didnt like it)

get a small hub or switch and connect the ethernet cable that is currently connected to your entertainment center computer to it. Then get 2 more cables, connect one of them from the hub/switch to your entertainment computer and then the other will be for your laptop (from the hub/switch to your laptop).

Thats about all I could find on how to do it googling, I wouldn't have a problem doing that if it were for my own practical use, but its not.
Obviously I'm on a wireless network, so I dont really NEED all the cables (except for one computer that doesn't have wireless - the entertainment center)

See my neighbor (who doesn't have the luxury of wireless) tried to set something similar up, and since I'm a bit more versed with computers and networking, came to me to help. I was a bit frustrated when I couldn't, so I decided to try and duplicate his attempted set up in my home to eventually come up with a solution.
The only other good lead I got was to set it up as I have it, and on the entertainment computer bridge the two connections to allow the passthrough, the only issue being that the internal IP set by the router is 192.168.x.xxx, I'm not positive how this works but somehow passing the connection through that computer brings it too "deep" I guess you would say, causing an IP conflict. My problem is I cannot even get the computer to recognize that there is a cable plugged into it. (I have checked to ensure that all network cards are operational.)

Referenced article: http://www.smallbusinesscomputing.com/webmaster/article.php/3303861

I do have access to change the internal IP of the router, I haven't done so yet as I don't want to muck up my entire network if it fails... I probably will end up trying that though once things "idle" down enough that I wont be interrupting too much traffic.

It seems to me that as you have set it up, it will never work. I am guessing the ethernet on the laptop as no IP assigned, as it wasn't assigned by any DHCP server. As I understand it, the only piece of network hardware that you have working on the laptop is the wireless adapter, so the ethernet adapter should have no IP assigned.
Richard's suggestion is the one that makes sense. Connect a hub to the wireless cable router, which will then server as a DHCP server to all the computers that you connect to that hub. Anything that you then connect to the hub will get an IP assigned by the wireless cable router and you will be able to use the internal connection to get the computers to talk to each other - each of them should have an IP of the type 198.0.x.x.

Your description is a bit unclear. How are you connecting to the internet? Do you have cable/dsl or some other broadband that's wired into a wireless router of yours with a LAN side ethernet switch, or are you using some kind of wifi Internet connection where your wireless router provides a wired LAN subnet?
If you're trying to wirelessly interconnect two segments of your internal LAN look into getting a WAP (wireless access point), like the old DLink 2100AP I used to use.

Originally posted by Da_Stimulator I have a 50ft ethernet cable running from it to my Entertainment center computer (hooked up to my tv & receiver for movies & music & such) - that works fine. I have internet on both computers. I installed another ethernet card on my Entertainment center computer in an attempt to run a cable from it to hook up to my laptop on an intermittant basis, but I cannot get this to work.
I've tried a regular ethernet cable and a crossover cable, both get the message (network cable is unplugged). I tried conneciton sharing, and bridging, but nothing seems to be working.

1. Get a small Netgear (or similar) 4-port 10/100 HUB. (less than $15 US and are quite small)
2. Connect 50ft Cat5 to UPLINK port of hub
3. Make sure UPLINK switch activated
4. Connect Entertainment Cntr to hub port using 'normal' cat5 cable
5. Connetc laptop to hub port using normal (NON-crossover) cable
6. Surf your **** off

Let me know if you have issues or need help finding hub.
Addendum: If you can get your hands on *any* hub, you can test this configuration. If it works, THEN get a small 4-port to tuck behind the Entertainment Cntr.
Edit: Modify to allow brands other than Netgear
Addendum

so I got it sorted, I found an old MS MN-100 router laying around, turns out you can switch it from router to bridge mode, and so that's what I'm using.

Your description is a bit unclear. How are you connecting to the internet? Do you have cable/dsl or some other broadband that's wired into a wireless router of yours with a LAN side ethernet switch, or are you using some kind of wifi Internet connection where your wireless router provides a wired LAN subnet?
If you're trying to wirelessly interconnect two segments of your internal LAN look into getting a WAP (wireless access point), like the old DLink 2100AP I used to use.

Neighbor has cable internet and a wireless router, I have a USB wireless modem (had an internal card but the antenna broke off...) that modem feeds my "good" computer as I call it, then I use the ethernet card off that to feed the router now with ICS, which allows me all the ports I need.

I'm glad you got it solved, it sounds liek a WAP connected to your neighbor's wireless would also do the trick for you without needing the ICS computer to be always on.

The ICS computer is always on anyway, even before I set up this connection. And now that I have it set up this way, its way more useful than my original "messing around" situation - now that I have wires in the living room, I can hook up my x-box, playstation 2, etc - along with having pandora radio and hulu video in my home theatre :)