Here:

The hard way by hand. Use PS's magic wand, the magnetic lasso or the color selector to get the large areas as close as possible. Delete the background. After that, pixel by pixel. Oh yeah, when you first open a picture it will put it on the background layer. You can't erase then.

1. Ctrl + A - Select all
2. Ctrl + C - Copy selection
3. Ctrl + V - Paste selection
This will put the same image on an actual layer that you can work with.
4. Do what I was saying at the top. Use the delete key to easily erase the selected elements. Then the eraser.

Hope that helps
Wyatt
ps. If you are using PSP, there are similar tools that do the same function, experiment. They just have different names.

Thanks.