Below is my script

$a = New-Object -comobject Excel.Application
$a.visible = $True

$b = $a.Workbooks.Add()
$c = $b.Worksheets.Item(1)

$c.Cells.Item(1,1) = "Organization"
$c.Cells.Item(1,2) = "Name"
$c.Cells.Item(1,3) = "Operating System"
$c.Cells.Item(1,4) = "IP Address"
$c.Cells.Item(1,5) = "MAC Address"
$c.Cells.Item(1,6) = "Service Packs"
$c.Cells.Item(1,7) = "System Type"
$c.Cells.Item(1,8) = "Install Date"
$c.Cells.Item(1,9) = "Manufacturer"
$c.Cells.Item(1,10) = "Model"
$c.Cells.Item(1,11) = "Service Tag"
$c.Cells.Item(1,12) = "Serial Number"
$c.Cells.Item(1,13) = "Number of Processors"
$c.Cells.Item(1,14) = "Total Phsyical Memory (GB)"
$c.Cells.Item(1,15) = "Last Reboot Time"
$c.Cells.Item(1,16) = "Report Time Stamp"

$d = $c.UsedRange
$d.Interior.ColorIndex = 19
$d.Font.ColorIndex = 11
$d.Font.Bold = $True

$intRow = 2

$cred = get-credential
$colComputers = get-content C:\computers2.txt
foreach ($strComputer in $colComputers)
{
$OS = gwmi -class Win32_OperatingSystem -Comp $strComputer
$Computer = gwmi -class Win32_ComputerSystem -Comp $strComputer
$Bios = gwmi -class Win32_BIOS -Comp $_
$IP = gwmi -class Win32_NetworkAdapterConfiguration -Comp $strComputer | where{$_.IPEnabled -eq "TRUE"}

$c.Cells.Item($intRow,1) = $OS.Organization
$c.Cells.Item($intRow,2) = $strComputer.Toupper()
$c.Cells.Item($intRow,3) = $OS.Caption
$c.Cells.Item($intRow,4) = $IP.IPaddress
$c.Cells.Item($intRow,5) = $IP.MACaddress
$c.Cells.Item($intRow,6) = $OS.CSDVersion
$c.Cells.Item($intRow,7) = $Computer.SystemType
$c.Cells.Item($intRow,8) = [System.Management.ManagementDateTimeconverter]::ToDateTime($OS.InstallDate)
$c.Cells.Item($intRow,9) = $Computer.Manufacturer
$c.Cells.Item($intRow,10) = $Computer.Model
$c.Cells.Item($intRow,11) = $Bios.serialnumber
$c.Cells.Item($intRow,12) = $OS.SerialNumber
$c.Cells.Item($intRow,13) = $Computer.NumberOfProcessors
$c.Cells.Item($intRow,14) = "{0:N0}" -f ($computer.TotalPhysicalMemory/1GB)
$c.Cells.Item($intRow,15) = [System.Management.ManagementDateTimeconverter]::ToDateTime($OS.LastBootUpTime)



$c.Cells.Item($intRow,16) = Get-date

$intRow = $intRow + 1
}
$d.EntireColumn.AutoFit()

Got error

Get-WmiObject : Cannot validate argument on parameter 'ComputerName'. The argument is null or empty. Supply an argument that is not null or empty and then try the command again.

Please help

Shouldn't this line:
be this?