PATH没有认识到它的添加

Question

C:\Users\jamiller>PATH
PATH=C:\Windows\Microsoft.NET\Framework\v4.0.30319;

C:\Users\jamiller>msbuild
'msbuild' is not recognized as an internal or external command,
operable program or batch file.

C:\Users\jamiller>cd C:\Windows\Microsoft.NET\Framework\v4.0.30319

C:\Windows\Microsoft.NET\Framework\v4.0.30319>msbuild
Microsoft (R) Build Engine version 4.0.30319.33440
[Microsoft .NET Framework, version 4.0.30319.34014]
Copyright (C) Microsoft Corporation. All rights reserved.

MSBUILD : error MSB1003: Specify a project or solution file. The current working directory     does not contain a project or solution file.

C:\Windows\Microsoft.NET\Framework\v4.0.30319> wat

任何人都知道为什么PATH无法识别其目录中的可执行文件？