Windows Live Messenger 2009出来啦，但是依旧默认不能同时开多个帐号，MSNShell依旧不支持新版本的MSN，我们只能手动修改注册表来多开MSN了！
方法很简单，因为Vista和WinXP的注册表基本类似，icech这里导出了一个WinXP下Windows Live Messenger 2009多开的注册表信息，你只需要导入进去就OK了！
经过测试在WinXP和Vista下均有效：
1、文件方式导入到注册表
打开文本编辑器，比如记事本。将以下蓝色文字拷贝进去，另存为MultiLive.reg，保存。然后双击此文件，将注册表信息合并。
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Live\Messenger]
"MultipleInstances"=dword:00000001
2、手动修改注册表
其实原理同上，只是手动修改一下。
开始->运行->输入regedit->找到
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Live\Messenger
增加一个新建DWORD值，名为MultipleInstances，数值数据为1。（如图所示）
修改后关闭注册表编辑窗口就可以了。这样就可以同时打开多个MSN登录不同的帐号了！如果你想卸载Windows Live Messenger 2009的话可以参考链接文章。
相关下载：Windows Live Messenger 2009正式版下载
原文：How To Enable Polygamy In Windows Live Messenger
Many of you will have several WLIDs, and want to sign into Messenger with more than one of them. Until now you had to seek refuge in a patch or add-on to be able to do so. Not anymore! Microsoft’s John Weisenfeld just shared a little trick with me to enable this, which I’m going to share with you.
The trick involves registry editing, so please follow these steps very carefully:
1. Start regedit (admin)
2. Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Live
3. Right click Messenger and create a new DWORD called MultipleInstances
4. Right click the newly added registry key and choose Modify
5. Set the Value data to 1
6. Close regedit
All done! Now you can launch Windows Live Messenger as many times as you want, and sign in with as many WLIDs you want, on one computer. Just don’t try to sign in with the same WLID more than once on one computer or it will throw error 80071392 at you!
原文地址：main/archive/2008/12/17/how-to-enable-polygamy-in-windows-live-messenger.aspx