I'm trying to connect my Linux (Ubuntu) computer though my laptop's internet, meaning my laptop (Windows XP) is connected to wireless internet and I'm connecting my Linux computer using an ethernet cable to my laptop. How do I set it up on my Linux and Windows computer? I've been trying but can't seem to get it working.
Exactly the same way you would share the connection with another Windows computer I would imagine. You'll probably just need to set up gateway information on the Linux computer if it isn't done automatically. I'd suggest you troubleshoot by getting a Windows computer to connect to the Windows laptop first, if you need help with that post in the Windows forums. I think you'll find that your problem is almost entirely to do with the laptop internet connection sharing setup, so to keep things simple don't involve Linux until you've proven how to do it in Windows first. To manually tweak things on Ubuntu if Windows is too crap to set things up with DHCP you'll need to right click the network icon in the tray and go through Edit Connections.
