Changing Xbox Live Gamertag: Does It Erase MW2 Data? No

No. Changing your Xbox Live gamertag does not delete or reset your Modern Warfare 2 (2009) progress.

Why

• Game saves, stats, unlocks, and leaderboards are tied to your Xbox Live Account (XUID), not your gamertag (display name).
• The gamertag is just a label; the underlying account ID remains constant.

What Happens

• Friends see new name instantly.
• In-game leaderboards update to new name.
• All MW2 data (rank, prestige, camos, challenges) stays exactly as-is.

Note: First gamertag change is free; subsequent changes cost $9.99 (varies by region).