[.net-4.0] Where is GACUTIL for .net Framework 4.0 in windows 7?

If you've got VS2010 installed, you ought to find a .NET 4.0 gacutil at

C:\Program Files\Microsoft SDKs\Windows\v7.0A\bin\NETFX 4.0 Tools

The 7.0A Windows SDK should have been installed alongside VS2010 - 6.0A will have been installed with VS2008, and hence won't have .NET 4.0 support.