Copy a row from 3000 excel files stored in a folder and paste it in a new workbook

I think the following change should do it for you:

From:

                ' Select row 2 of the worksheet, and copy it to the first empty row on the 'summary' worksheet
                input_ws.Rows(2).Copy Destination:=.Rows(Output_Row)

To:

                ' Select row 2 of the worksheet, and copy just the values to the first empty row on the 'summary' worksheet
                input_ws.Rows(2).Copy
                .Rows(Output_Row).PasteSpecial Paste:=xlPasteValues

Hope that helps