When you try to install Powershell 2.0, you are prompted to uninstall other versions of Powershells before going ahead with the installation. But neither does powershell appear in Add/Remove programs nor is there an uninstall shortcut in the programs menu.

To uninstall powershell 1.0 run add/remove programs (appwiz.cpl from Win+R) and click the “show updates” checkbox. Powershell will now be shown.

[http://geekzguru.wordpress.com/2008/02/16/howto-uninstall-powershell-10/]