That's an interesting issue you have there...slow network connectivity. *thinks* What I would do as basic troubleshooting steps is, uninstall everything. The NIC in the device manager, remove the TCP/IP protocol bound to it. With everything uninstalled, reboot the machine and allow it to find the NIC itself. Once it is found, go ahead and re-install TCP/IP to the NIC. This will ensure that everything is fresh.
If your connection is still slower then what it was originally, the only thing I can think of is something on the computer. Watch the stat's for packets coming in and going out as your trying to browse the internet with it. See if it's sending and recieving at a stable increase. Also make sure you don't have any spyware that may be using your network rescources. GAIN and other's are known to do that.
That's what I would do.
"Why are we necessary?"
"Only to rise up to the challenge"
-Macross Plus-