To install Windows PowerShell v2 CTP 3 do the following.
1. Open the Control Panel and select "Uninstall a program"
2. When the Uninstall window opens select "Turn Window features on or off".
3. When the Window Features dialog opens, find "Windows PowerShell" and remove the check in the check box.
4. Click on the OK button. This operation will take a few min before it closes.
5. Now install the new version of PowerShell v2 CTP 3
6. Once it is installed you are done.
Warning: Do NOT go back and enable the feature, that action will reinstall the older version.