Please help...

If all computers are useing the internet it will be limited because they will have to share the download and up load speed. If it wont go on the internet at all reinstall you computer back onto the wireless next work.

I don't know too much about this but I have seen more than 3 wireless connections and a main connection being done without any problems. If I had to take a guess, I would check the Network configuration on the computer that connects to your ISP. It could be limiting the amount of connections.

I don't think it is because of that. it may be either your new computer is not set to share internet connection. you can make it check from computer properties. it might be problem of two different OS like XP and Vista too..

Maybe... Wireless connection sometimes commit many errors... I advise that you should change your connection ito a cabled internet not wireless...

As far as I know, since I am using a wireless router with sometimes up to 8 computers connected, bandwidth is not the issue here. If the third computer is using up too much of the bandwidth, the other computers will experience a slow download and upload speeds. Is the second computer still receiving the radio signal?

Access your router, and check the firewall settings. I could be wrong in this case, but there is nothing to lose in making a check.

Another alternative is to change the radio channel.

Your problem is very easy my friend. Just check your IP address. The reason about this is the duplication of IP, and you need to configure you IP address. There is no connection of whether there is new computer you have or download in what ways. If you have static IP, please fixed your IP addresses each computer...

you are facing an ip address conflict.. since they are in same network.. try giving them different static ip address.. usually 192.168.1.2, 192.168.1.3, 192.168.1.4 if you want it to be configured in class c network..