1. Take your profile out of your harddrive using Xporer360 or Xport360 and put it onto somewhere like your Desktop.
(Partition 3>Content>Profile ID>FFFE07D1>0010000>E000010something)

2. Open your profile in HxD (Hex Editor).

3. Search for your current clantag using Text-String, NOT Hex Values, etc.. (Obviously).

4. So mine is like HAHA or something like that. Then replace that with the one you want like F**K or C**T or NAZI, basically anything like that. But I would NOT do Nazi as M$ takes Racism very seriously.

5. Once you are done, save your profile.

6. Then find it on your desktop, not your .BAK (backup profile). Your original one.

7. Open hashblock calculator, then open your profile. Calculate hashblocks.

8. Drag it back into xport360/xplorer360 and overwrite the old one then your done.

9. Load up MW2, go to multiplayer.

10. ENJOY YOUR NEW CLANTAG.

Programs:
Hash Block Calculator - MEGAUPLOAD - The leading online storage and file delivery service
Xport360 - XPort 360 Software Informer: Latest version download, news and info about this Datel program.
Xplorer360 - [ Register or Signin to view external links. ]
Hex Editor - Freeware Hex Editor XVI32
Xbox 360 Transfer Cable or whatever you use - Buy It Yourself!