客户现场，安装sqlserver 2008R2；因为情景需要，客户指定了一架在用的笔记本在预演。
突然遭遇了从来没有的问题：
A network error occurred while attempting to read from the file C:..\..\sqlncli.msi 如图。
因为距离下班时间很近了，很着急也很恼火，捣鼓来捣鼓去，最后打开了控制面板，一看，妈呀好多SQL Server的东东，挨着删除吧。。。居然就可以安装了了。。。。
最终发现如果任何 SQLNCLI或者Native Client存在了，就会出现这个问题。
Microsoft大哥居然弄了这么黑的一招。。。
同时看到有人遭遇了类似的悲剧：
Finally got the Client Tools and Mangement Studio installed. What I did was remove Microsoft SQL Server 2008 Native Client in Add or Remove Programs (before I was just trying to uninstall Microsoft SQL Server 2008 and it failed). After Native Client was removed, I reinstalled client tools and mangement studio from a dvd (was mounting the iso before). Everything installed perfectly.
这个人解释的更多：
The cause of the error
I wondered what was different between my clean test-VM and my server that I was now attempting to install SQL-SERVER 2008 R2 Client Tools and SSMS onto. Both were 64-Bit OS's and same setup, etc., but one was a clean VM. This got me thinking
I had PREVIOUSLY installed JUST the SQLNCLI (SQL-Server Native Client)
for SQL 2008 R2 onto my physical system, in order to test application connectivity to a SQL2008R2 database. So, could that be it!? YES! After uninstalling any previously installed SQLNCLI applications, and re-running the SQL-Server installer, amazingly my "network errors" were gone and the installation was fixed!
Microsoft: GIVE MEANINGFUL ERROR MESSAGES! All the installer had to
do was say that "previous installations of SQLNCLI / native client exist and must be removed before installing"
in fact, the PREREQUISITES-CHECK SHOULD HAVE TESTED FOR THIS
if it can cause a total failure to install!