diff --git a/MainForm.ps1 b/MainForm.ps1
index 56104ad..a6dcfe5 100644
--- a/MainForm.ps1
+++ b/MainForm.ps1
@@ -2,6 +2,15 @@ Add-Type -AssemblyName System.Windows.Forms
 Import-Module Microsoft.Graph.Sites
 Import-Module Microsoft.Graph.Files
 
+# Load Open XML assembly
+try {
+    Add-Type -Path "C:\Program Files\Microsoft Office\root\Office16\DocumentFormat.OpenXml.dll"
+}
+catch {
+    [System.Windows.Forms.MessageBox]::Show("Error loading DocumentFormat.OpenXml.dll. Make sure it is installed.")
+    return
+}
+
 # Import our components
 . "$PSScriptRoot\GraphConfig.ps1"
 . "$PSScriptRoot\SharePointFunctions.ps1"
diff --git a/SharePointFunctions.ps1 b/SharePointFunctions.ps1
index 78b942b..62b310b 100644
--- a/SharePointFunctions.ps1
+++ b/SharePointFunctions.ps1
@@ -1,3 +1,5 @@
+# SharePointFunctions.ps1
+
 # Load configuration from config.json
 function Load-Config {
     try {
@@ -75,7 +77,6 @@ function Get-FolderBrowser {
         # Get root folder first
         if ($ParentFolderUrl) {
             # Get the folder ID first
-            # Construct the correct URI for the folder
             # Remove the /sites/tax/Shared Documents/ part from the folder path
             $relativePath = $ParentFolderUrl.Replace("/sites/tax/Shared Documents/", "").TrimStart("/")
             
@@ -392,5 +393,110 @@ function Get-XlsFilesCurrentFolder {
 }
 
 function Convert-Files {
-    $script:txtStatus.Text += "Convert-Files function called (placeholder).`n"
+    try {
+        # Load the file list from the JSON file
+        $fileListPath = "$env:TEMP\FileList.json"
+        if (Test-Path $fileListPath) {
+            $fileList = Get-Content $fileListPath -Raw | ConvertFrom-Json
+        } else {
+            $script:txtStatus.Text += "Error: FileList.json not found. Please list files first.`n"
+            return
+        }
+
+        # Check if the file list is empty
+        if ($fileList.Count -eq 0) {
+            $script:txtStatus.Text += "No files to convert.`n"
+            return
+        }
+
+        # Iterate through the file list and convert each file
+        foreach ($file in $fileList) {
+            $originalPath = $file.OriginalPath
+            $originalFileName = $file.OriginalFileName
+            $tempPath = $file.TempPath
+
+            $script:txtStatus.Text += "Converting file: $originalFileName`n"
+
+            # Download the file from SharePoint
+            $downloadPath = "$env:TEMP\$originalFileName"
+            try {
+                # Extract DriveId and ItemId from the originalPath
+                if ($originalPath -match "drives/([^/]+)/items/([^/]+)") {
+                    $driveId = $matches[1]
+                    $itemId = $matches[2]
+                } else {
+                    throw "Could not extract DriveId and ItemId from OriginalPath"
+                }
+                
+                # Download the file
+                $fileContent = Invoke-MgGraphRequest -Uri "https://graph.microsoft.com/v1.0/drives/$driveId/items/$itemId/content" -Method GET -OutFile $downloadPath
+                if (-not (Test-Path $downloadPath)) {
+                    throw "Failed to download file from SharePoint"
+                }
+            }
+            catch {
+                $script:txtStatus.Text += "Error downloading file: $($_.Exception.Message)`n"
+                continue # Move to the next file
+            }
+
+            # Convert the file to XLSX
+            $xlsxFileName = $originalFileName -replace "\.xls[m]?$", ".xlsx"
+            $xlsxPath = "$env:TEMP\$xlsxFileName"
+            try {
+                # Open the Excel file
+                $excel = New-Object -ComObject Excel.Application
+                $excel.Visible = $false  # Keep Excel hidden
+                $workbook = $excel.Workbooks.Open($downloadPath)
+
+                # Save as XLSX
+                $workbook.SaveAs($xlsxPath, 51)  # 51 is the code for XLSX format
+                $workbook.Close()
+                $excel.Quit()
+
+                # Clean up COM objects
+                [System.Runtime.InteropServices.Marshal]::ReleaseComObject($excel) | Out-Null
+                [System.Runtime.InteropServices.Marshal]::ReleaseComObject($workbook) | Out-Null
+                Remove-Variable excel, workbook
+
+                $script:txtStatus.Text += "Successfully converted to: $xlsxFileName`n"
+            }
+            catch {
+                $script:txtStatus.Text += "Error converting file: $($_.Exception.Message)`n"
+                continue # Move to the next file
+            }
+
+            # Upload the converted file to SharePoint
+            try {
+                # Get the Drive ID and destination folder
+                $destinationFolder = $script:txtTempLib.Text
+                $uploadUri = "https://graph.microsoft.com/v1.0/drives/$driveId/root:/$destinationFolder/$xlsxFileName:/content"
+                
+                # Read the file content
+                $fileContent = [System.IO.File]::ReadAllBytes($xlsxPath)
+                
+                # Upload the file
+                Invoke-MgGraphRequest -Uri $uploadUri -Method PUT -Body $fileContent -ContentType "application/octet-stream"
+                
+                $script:txtStatus.Text += "Successfully uploaded to SharePoint: $destinationFolder/$xlsxFileName`n"
+            }
+            catch {
+                $script:txtStatus.Text += "Error uploading file: $($_.Exception.Message)`n"
+                continue # Move to the next file
+            }
+
+            # Clean up temporary files
+            try {
+                Remove-Item $downloadPath -ErrorAction SilentlyContinue
+                Remove-Item $xlsxPath -ErrorAction SilentlyContinue
+            }
+            catch {
+                $script:txtStatus.Text += "Error cleaning up temporary files: $($_.Exception.Message)`n"
+            }
+        }
+
+        $script:txtStatus.Text += "File conversion complete.`n"
+    }
+    catch {
+        $script:txtStatus.Text += "Error in Convert-Files function: $($_.Exception.Message)`n"
+    }
 }