Let's pick one interface at a time, either wired or wireless. Since wired LAN issues are usually less complicated, I'd suggest to pick it first. Then, when it gets resolved (or if we give up on it ) we can pick the wireless one.
So, in order to find the answer to your misery , we need details which the outputs of the following commands may provide:
[Note: Do some browsing first for a couple of minutes, then enter these commands in a terminal one-by-one]
Wrap each set of output in [ code] and [ /code] tags as described here for better readability.
sudo lshw -C network
(or any site which appears painfully slow in comparison to windows)
Also, how do you connect to internet? If it is an adsl modem/router, which brand and model? There have been some models whose firmwares had been reported to cause problems with linux kernel in the past.