Here is a tutorial on how to set your clan tag to unbound or whatever you want as long as it's 4 characters on Call of Duty: Modern Warfare 2.

READ: You will need to have a 4 character clan tag on MW2 before you copy your profile.

Things you will need:
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Yep. This program is so cool it's all you need.

Steps:
1. Copy your profile from your xbox to your usb.
2. Open up Hadzz, IT HAS TO BE WITH EVERYTHING IN THE .ZIP TO WORK.
WARNING: Hadzz won't work for me for some reason, everytime I open it up it takes me to a web page and says invalid liscense, if you have same problem, turn off your wi-fi and it'll work with all VIP features.
3. Open USB and find your profile.
4. Go to the Clan Tag tab, and select the radio button, Your Profile.
5. Edit your clan tag to what you want it to be, if you want it to be Unbound then but illegal characters like { } or @@.
5. After you are done modding your clan tag hit the Save button.
MAKE SURE IT IS SET TO YOUR PROFILE IF YOU WANT IT TO BE ON YOUR PROFILE
6. Click the MW2 emblem in the top left corner and hover over save, and click USB, it'll save, rehash and resign automatically, then move your profile back to your xbox and start up MW2.
7. Congrats, your clan tag is now modded, if you have any questions or if it didn't work just post below.