Esperento57's script doesn't work in older PowerShell versions. This example does:
Get-ChildItem -Path "C:\temp" -Recurse -force -ErrorAction SilentlyContinue | where {($_.LastwriteTime -lt (Get-Date).AddDays(-15) ) -and (! $_.PSIsContainer)} | select name| Remove-Item -Verbose -Force -Recurse -ErrorAction SilentlyContinue