下面的英文是从MapObject的readme中复制来的，从中可以找到出现这个问题的原因所在：就是MapObject的安装能自动探测到.NET Framework and SDK version 1.0 and 1.1，而现在的版本一般是2.0的，所以需要自己设置路径。你需要将其定位到含有Gacutil.exe 文件的文件夹，比如我现在的路径就是C:\Program Files\Microsoft Visual Studio 8\SDK\v2.0\Bin，设置后就可以继续安装了，安装完成后还会安装帮助。
The MapObjects installation program will be able to detect the location of both the version 1.0 and 1.1 of the Framework and SDK. If you install MapObjects to a version of the .NET Framework later than 1.1, you will be given the opportunity during the install to locate the Framework yourself, so that the MapObjects SDK for .NET can be installed. In this case, you will need to locate the folder containing the Gacutil.exe file, which is part of the .NET Framework SDK. In versions 1.0 and 1.1 of the .NET Framework SDK, Gacutil.exe can be found in:
\<Microsoft Visual Studio .NET install folder>\SDK\<version number>\Bin
However, Microsoft may change this location in future versions, in which case you can search manually for the Gacutil.exe file.
When you install the MapObjects SDK for .NET, you will be given the option to install MapObjects help files for Visual Studio .NET; these help files will then be available within
