CriticalSystemErrorsLastMonth.ps1

$filterXml = '<QueryList>
      <Query Id="0" Path="System">
        <Select Path="System">*[System[(Level=1 )]]</Select>
      </Query>
    </QueryList>'

$pcs = (Get-ADComputer -Filter * | ? { Test-Connection $_.DNSHostName -Quiet -Count 1 }).DNSHostName

$pcs | % {
    Get-WinEvent -FilterXml $filterXml -ComputerName $_ | ? TimeCreated -GT (Get-Date).AddMonths(-1)
} | Select MachineName, TimeCreated, ProviderName, Id, Message | Out-GridView -Title "Critical System Errors Last Month"