Having problems upgrading your old PowerShell 1.0 installation to the 2.0 CTP? The CTP won’t install until you’ve uninstalled all previous versions of PowerShell, but lots of people are having problems figuring out how to uninstall v1.0.
The official docs tell you to click on the “Show updates” checkbox in the Control Panel Add/Remove Programs applet, but that didn’t work for me. “Windows PowerShell 1.0″ (or any variation thereof) didn’t show up.
A google search led me to look for installed service packs in the %WINDOWS%\$NtUninstallKB* directories that has the “PSCustomUtil.exe” file in them. Then go to the child /spuninst/ directory and uninstall the KB that way. I got a ton of warnings saying I would nuke my system back to the Stone Age should I attempt the treasonous act of actually uninstalling a KB patch, but I – being the renegade that I am – went ahead and did it anyway.
My search picked up two KB packs: KB926139-v2 (Windows PowerShell 1.0), and KB926141 (Windows PowerShell MUI).
Once I uninstalled both, I was able to successfully install the PowerShell v2 CTP3.
Hope this helps you too.