Get-ChildItem -Path .* -Recurse -File |
    Where-Object{$_.Extension -and $_.BaseName -like "*$($_.Extension)"}

Get-ChildItem -Path .* -Recurse -File |
    Where-Object{$_.Extension -and $_.BaseName -like "*$($_.Extension)"}|
        Rename-Item -NewName {$_.BaseName} -WhatIf

Get-ChildItem -Path .* -Recurse -File -Exclude "C:Windows" -EA SilentlyContinue|
    Where-Object{$_.Extension -and $_.BaseName -like "*$($_.Extension)"}