Visual basic : Generic GDI+ error when saving file - vb.net

Question

When I executed my program I created in visual basic. I got a GDI+ error when I tried to save an image from a picturebox.
If I run it on the PC, where I created the program(windows 10), I don't have any problems. When I run it on 2 different windows 7 PC's, I got the error.
The mapped networkdrive is the same ( Z:\ ) and writeable.
Here is the code:
Private Sub SaveImage(ByVal pathToSaveTo As String)
Try
Using bmp As New Bitmap(Picimage.Image)
bmp.Save(pathToSaveTo, Drawing.Imaging.ImageFormat.Jpeg)
End Using
Catch ex As Exception
MessageBox.Show("An error occurred:" & vbCrLf & vbCrLf & _
ex.Message, "Error Saving Image File", _
MessageBoxButtons.OK, MessageBoxIcon.Asterisk)
End Try
End Sub
The button to start the action
Private Sub Button2_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Dim dt As String = My.Computer.FileSystem.SpecialDirectories.Desktop
Dim testOutput As String
testOutput = "Z:\" & naam & " " & Now.ToString("HH/mm/ss") & ".jpg"
SaveImage(testOutput)
nr.Focus()
End Sub

Answer 1

GDI is complaining about the filename you're using.
Here's the problem: testOutput = "Z:\" & naam & " " & Now.ToString("HH/mm/ss") & ".jpg"
You're generating a filename with slashes in the path. If those are meant to be directory names (a directory for each hour, minute and second respectively) then those directories need to ex that won't work as GDI will not create missing directories along a path for you. If the slashes are meant to be in the filename itself then it also won't work as slashes are not a valid filename character.
Change the slashes to underscores or hyphens or other characters allowed in filenames:
testOutput = "Z:\" & naam & " " & Now.ToString("HH_mm_ss") & ".jpg"