I mentioned the release of PowerShell at:
If you have a previous version of PowerShell installed, the Setup program will NOT install PowerShell 1.0.
If you are unable to uninstall the previous version, you can:
1. Open a CMD.EXE window.
2. Type the following command and press Enter:
REG DELETE HKLM\Software\Microsoft\PowerShell\1 /V Install /F
NOTE: REG.EXE is built into Windows XP, Windows Server 2003, and later operating systems, or installed from the Windows 2000 Support Tools.