Rename files with Power Shell

Remove extension:

gci *.deploy |%{rename-item $_.fullname -newname $_.basename}

Rename replace with expression:

gci *.jpg | rename-item -newname {$_.name -replace '^','ico_'}

Check results with whatif:

gci *.deploy |%{rename-item $_.fullname -newname $_.basename -whatif}
gci *.jpg | rename-item -newname {$_.name -replace '^','ico_'} -whatif

Source