To disable the wire less:
Firstly, there may be a hardware switch on the front of the laptop (depends on brand).
There should also be a software method. One of the icons in the systray (bottom right of the screen) should show the wireless connection. You may be able to right click and select "disable". But the laptop may use a propriety software like "Toshiba Connection Manager". You will have to find it in the Start-Programs menu and select "wireless off".
If you are on ADSL and pinging over 100 to a local server you DO NOT need to upgrade your connection. But you sure as hell need to call your provider and ask them WTF is wrong with your connection. One of the issues with ADSL is that if you have a crappy phone line, you have a crappy Net connection.
No way should you be getting that kind of crapola performance from an ADSL connection. Another thing you should try is to log on to Speedtest from one of the other machines in the household and test the ping. Process of elimination. Your machine might have issues.