SharePoint 2010 SDK Downloads
We just refreshed the downloads of the SharePoint SDKs on the Microsoft Download Center to reflect the many recent updates and enhancements to the documentation since RTM. You should first uninstall any previous versions of the SDK installed on your machines through Control Panel.
Get the updated SDKs today!
Office SharePoint Server 2007 SDK (Version 1.1)
Installs to %SystemDrive%\2007 Office System Developer Resources\SharePoint Server 2007 SDK\
Windows SharePoint Services 3.0 SDK (Version 1.1)
Installs to %SystemDrive%\Windows SharePoint Services Developer Resources\Windows SharePoint Services 3.0 SDK\