Usually most of the software you install has an uninstall option in the program menu from where you can easily uninstall the software, but with some softwares like Windows Media Player 11 and Internet Explorer 7 it is not the case.
"!!MUST REBOOT THE WINDOWS PHONE AFTER INSTALL!! !!Before installing, please be sure to manually uninstall any existing version of Windows Live prior to version 11.!! Now you can stay connected to those that matter most with Windows Live™ for Windows® phone. Windows Live Messenger, Hotmail®, Photos and the “What’s New” feed are now all available on your 6.x Windows Phone.”"
http://marketplace.windowsphone.com/details.aspx?appSKU=8c4f17d2-59e0-44...
Sometimes you may encounter problems in uninstalling old version of live messenger when you might want to upgrade it to the newer version or you just want to get rid off your computer. But when you try to remove it with the usual Configuration – Add/Remove software steps, it might not even appear in the list, while the setup of the WLM says it is all ready installed.
We promised you a look at Windows Live Messenger 2010 earlier this week when we revealed Microsoft is planning both Bing and Messenger iPhone applications next year.
IT major Microsoft has recently said that its popular messenger platform MSN would retire and be replaced by already available new IM in the Windows Live Hotmail.