BleepingComputer.com: cannot connect to DSL cable

hi guys! my laptop is a dell inspiron 1200. my problem is that i cant connect to the internet using a DSL cable at home or anybody's house. i dont know why. i tried connecting with my firewall turned off, and even tried unplugging all the cables for the DSL and restarting my laptop but to no avail... however, i can easily connect to wireless connection anywhere. and i can also connect to my school's DSL connection without any problem. but if it's a house DSL connection, i cant really connect.. please help me... what troubleshooting stuff can i do to make it work?