Powershell, Sort a list of files by version number at the end of the filename?

You can use the [Version] type to do the version sorting. This only takes the version into account (so it doesn't care about the beginning of the filename):

dir $_ |
    Sort-Object { 
        [Version] $(if ($_.BaseName -match "(\d+_){3}\d+") { 
                        $matches[0] -replace "_", "."
                    } 
                    else { 
                        "0.0.0.0"
                    })  
    } | select -last 1 -ExpandProperty Name

There may be a better way, but this works:

Get-ChildItem $_ | 
    Sort-Object {[int]$_.Name.Split("_")[2], [int]$_.Name.Split("_")[3], [int]$_.Name.Split("_")[4], [int]$_.Name.Split("_")[5]} -Descending |
    select-object -First 1 -Property:Name