To activate Windows 7 Build 6469 , you should use a Windows Vista retail product key

One humid evening, a contact slipped him a relic: a dusty, heat-warped DVD-RW with "Win7 6469 x86" scrawled in permanent marker. The label was smeared, but Leo recognized the numbering immediately. Windows 7 Build 6469. A pre-beta, compiled in late May 2008, rumored to contain the ghost of a canceled interface codenamed "Milan." It had never leaked. Most collectors thought it was a myth.

Alternatives

2. Common "Beta" Keys May Not Work You will find lists online of "universal" Windows 7 beta keys (e.g., those for Build 7000 or 7600). Do not expect these to work on Build 6469. Microsoft changed the hashing algorithms for product keys between milestones. A key for the Beta (Build 7000) or RC (Build 7100) will almost certainly be rejected by the installer for Build 6469.