### Finds all xls files in a given folder and then checks to see if an xlsx copy of the file already exists before converting.
### Optional flags below can be set to remove the xls file while gathering the list of files and/or after converting.

# Search Folder and SubFolders
$Recurse = $true

# If xls and xlsx verions of the same file exists - remove xls file
$RemoveOriginalOnCheck = $true

# Remove orignal xls file when xlsx is created
$RemoveOriginal = $true

## Path to excel documents
[System.IO.DirectoryInfo] $FolderPath = "C:\Users\landonl\Desktop\New folder"

Add-Type -AssemblyName Microsoft.Office.Interop.Excel
$xlFixedFormat = [Microsoft.Office.Interop.Excel.XlFileFormat]::xlOpenXMLWorkbook

Write-Progress -Activity "Converting XLS to XLSX" -Status "Gathering Files from $FolderPath" -PercentComplete 0
if($Recurse){$Files = Get-ChildItem -Path $FolderPath -Recurse}else{$Files = Get-ChildItem -Path $FolderPath}
$Files = $Files | where {$_.Extension -eq ".xls"}

$FileCount = 0
$FilesToConvert = $Files | Foreach {
$FileCount++
Write-Progress -Activity "Converting XLS to XLSX" -Status "Checking to see if a xlsx copy exisists in the same folder for $_.Name" -PercentComplete (($FileCount / $Files.Count)  * 100)
[System.IO.FileInfo] $SaveAs = $_.FullName.Split(".")[0] + ".xlsx"
if($SaveAs.Exists -eq $false){$_}else{
Write-Host "$SaveAs already exists"
if($RemoveOriginalOnCheck){Remove-Item $_.FullName}
}
}

#Open Excel
$excel = New-Object -ComObject excel.application
$excel.visible = $false

#Start Converting Files
$FileCount = 0
$FilesToConvert| Foreach {
$FileCount++
Write-Progress -Activity "Converting XLS to XLSX" -Status "Saveing $_.Name as XLSX" -PercentComplete (($FileCount / $Files.Count)  * 100)

$SaveAs = $_.FullName.Split(".")[0] + ".xlsx"

$workbook = $excel.workbooks.open($_.FullName)
$workbook.saveas($SaveAs, $xlFixedFormat)
$workbook.close()

if($RemoveOriginal){Remove-Item $_.FullName}

}

#Close Excel
$excel.Quit()
$excel = $null

[gc]::collect()
[gc]::WaitForPendingFinalizers()