The latest version of FXCop (v10) is bundled with the install of the latest Windows SDK for Windows 7 and .Net 4, released on 5/19/2010. From Microsoft – Full ISOs
Once the SDK is installed you can find the FXCop installer EXE under %programfiles%\Microsoft SDKs\Windows\v7.1\Bin\FXCop (This assumes you kept the default install directory when installing the SDK).
Enjoy.