Here is a tutorial on how to connect Xbox 360's HDD on PC and also.
You can do anything you want with this HDD, but i am showing how to play Xbox's Live games, too.
Most games will be as "Trial", while few of them don't run at all, unless you jtag the Xbox.
To avoid all this, you can buy this USB Hard-Drive Transfer Kit, which costs ~$7, but if you are a DIY fan, keep reading :)
How to Remove the HDD. You will 3 screws on it (the 4th is under the label). Unscrew them and remove the cover.
Now unscrew the 4 big screws. You can remove them easy with a nipper or something similar. When remove the metal cover, you will see the HDD inside. Unplug the cable and take it out.
Now you can connect the HDD on your PC, like any other HDD.
Windows will recognize the HDD immediately.
Now run the Xloper360. In the first screen, go to menu and select "Open -> Harddrive". You will see the HDD's data. Go to "Partition3" and it will show you its contents.
Look on the "0000000000000000" folder, inside the "Content". The folders on right, are the demos of Xbox360.
To add a new game, right click anywhere inside "0000000000000000" folder and select "Insert Folder". Repeat until you have the games you want.
When done, connect the HDD back to Xbox. Turn it on and go to Games and then to [Xbox Live Arcade]. You will see the games you selected.
Xbox Live games you can find in many torrent sites. Below are Chessmaster and Contra.