Net Framework 4.0 和.Net Framework 4.0 Client Profile区别：

.Net Framework 4.0毫无疑问就像是.Net Framework 2.0一样是.Net Framework 的 4.0版本；

而.Net Framework 4.0 Client Profile是.Net Framework 3.5 sp1的子集，是.Net Framework 4.0 简化版，

是面向客户端应用程序的（估计这也是为什么不能够使用IIS7 API的原因）。

什么要引入这个简化版本呢？

1. 减少.NET Framework以及包还.NET Framework的应用程序的部署时间；
2. 减少.NET Framework部署的失败；
3. 减少.NET Framework在ISV软件的所占大小，从而给其软件更多的空间；
4. 减少安装了.NET Framework Client Profile的系统受攻击的“界面”，因为Client Profille中部包括ASP.NET和一些服务器所要的组件；

When to use NET4 Client Profile and when to use NET4 Full Framework?

Client Profile: 
We recommend that the NET4 Client Profile be utilized as the primary framework for most client desktop applications (including Windows Forms and WPF apps). 
Since we are considering to make the NET4 Client Profile available broadly to desktops via Windows Update, most client desktops may have NET4 Client Profile soon after NET4 releases making it ubiquitous*. 
Until that time, NET4 apps can chain-install the NET4 Client Profile which is smaller and faster to install.

*Note: This plan is not final.

Full framework: 
The Full framework is a superset of the Client Profile. It should mainly be used for:

Server apps (e.g. ASP.Net apps) For developer scenarios (for example, this includes msbuild) For all other legacy client scenarios (for example, this includes System.Data.OracleClient.dll which is being deprecated in NET4) that are not included in the Client Profile.