最后找到一个修改注册表的方法，
The following set of instructions is ONLY for these Inspirons models:
B120, B130/1300, 6400/E1505, 9400/E1705, E1405/640m, XPS M140/630m and any others with the Sigmatel 92xx HD chip & driver.
On these models that have the Sigmatel 92xx audio chip, monitoring can be restored by editing the Registry subkey EnableInputMonitor.
[It is wise to create a System Restore point before editing the Registry! If you accidentally make incorrect edits to the Registry you could cripple your computer, but using System Restore should correct any problems. To create a new Restore Point go to Start/Help & Support/System Restore and tick 'Create a restore point'. Even better is to save a backup copy of the Registry by using its 'Export' utility.]
Go to the Start menu and click on Run. Type "regedit" without quotes and click OK to open the Registry.
At the top of the list, highlight My Computer.
Under the Edit menu, select Find.
Type in "EnableInputMonitor" without quotes and click 'find next'.
Highlight EnableInputMonitor. Right click on it and select Modify.
Highlight 00 and change to 01. Click OK.
Repeat "find next" (F3) several more times and keep changing values to 01 until the EnableInputMonitor's coming up are of the proper value.
Find a key named "EnableIntSpkrMute" and change its value from 01 to 00.
Exit the Registry and restart the computer.
Next, configure the system mixer:
Open Volume Control by right clicking on the speaker icon on the taskbar and clicking 'adjust audio properties', or go to Start/Control Panel/ Sound & Audio Devices Properties/Advanced (button).
Under the Options menu, select Properties.
Under 'show the following volume controls' check the box next to Input Monitor. Click OK.
Make sure the mute box is unchecked. Unfortunately the slider itself will be frozen in place and won't control the outputted volume.
NOTE:
This Registry edit was discovered by emann15 who gave it to the forum, and The Performing Flea added some necessary modifications. I have put it into this step-by-step format for those of us who are not familiar with editing the Registry. This is the direct Registry path to the key:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{4D36E96C-E325-11CE-BFC1-08002BE10318}\0005\Settings\filter
\Rear
是解决了出声问题，但音量不受控制，全部静音也不起作用。继续搜索资料，终于找到更好的方法了，就是LG笔记本中的SigmaTel声卡驱动，下载安装完成，完美解决问题。
带立体声混音的声卡驱动程序,6400一样可以,相信我的就下吧!
驱动实在是太大了,,也可以自己去下....
请到如下网站
http://www.lge.com/support/software.jsp
选择地区(Your location)
比如：asia，HongKong
然后选择搜索框中的
Product: NOTEBOOK
并在subject中填写: SIGMATEL
然后搜索，出的结果是3个，选择最大的哪个文件，文件名为：SIGMATEL.zip (大约92M)
下载完了解压缩，然后setup
到此已经完成全部操作。
