Unblock a file with PowerShell?

Question

I am trying to have PowerShell unblock a file in Win2K8 R2.

Does anyone have a pointer as to the syntax?

Answer 1

Oneliner to remove zone informarion(inspired by accepted answer) for all children (with correct quoting).

get-childitem -rec | % { cmd /c "echo.>""$($_.FullName)"":Zone.Identifier" }

Not strictly answer to the question, just want to make sure when I next come up with this problem there is solution already :).

PS. Works in PS 2.0