一、如果安装过多个实例，必须彻底卸干净再重装，否则 Management Studio装不上。办法是这样的：
1. Uninstall the existing SQL Server 2008 R2 Express Edition and all the components from the control panel. Remember to back up the user databases before uninstalling SQL Server.
2. Backup the registry.
3. Delete the following keys in “regedit.exe”:
--HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server
--HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSSQLServer
4. Go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall and delete all the sub-keys referencing SQL Server.
5. Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services and delete all the keys referencing SQL Server.
6. Rename all the SQL Server folders in the computer.
7. Download and install Windows Cleanup Utility:
_http://support.microsoft.com/?id=290301
Run the utility and remove any SQL Server components that you find.
8. Reboot the machine
9. Delete remaining files manually.
二、如果安装了 visual studio 2008，则必须升级到 SP1
三、安装的时候不要直接运行，要解开到一个目录下面，然后到子目录下面找到 sqlsupport.msi 先安装一次，然后再重新运行 setup。（这真是太绝了，微软啊微软，如果不是老子赶时间没时间鼓捣mysql，我就一拳砸烂你个臭狗屎数据库）