Here are a couple of examples of registry hacks I've added during OSD Deploy task Sequences on a 64-bit Windows 7 systems:
cmd /c "reg add HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon /v DefaultDomainName /t REG_SZ /d MyDomain /f"
The below requires the Disable 64-bit file redirection option select as the commands execute in 32-bit mode by default.
cmd /c "reg add HKCR\CLSID\{<some GUID>}\Instance\InitPropertyBag /v Param1 /t REG_SZ /d http://intranet /f"