Sometimes, Excel documents created on older computers or versions of Excel become unstable on newer versions; similarly, Excel documents can be saved in many different file formats. By changing the Excel file format to "xlsx" (or "xls" for older programs), you can fix this problem. Click the Windows logo in the bottom-left corner of the screen. Click the folder-shaped icon in the lower-left side of the Start window. It's at the top of the File Explorer window. A toolbar will appear below this tab. This option is in the "Show/hide" section of the toolbar. Doing so will allow you to see the file type extensions at the end of files, including your Excel document. Go to the location of the Excel document that you want to recover, then click the document to select it. It's a tab in the upper-left side of the File Explorer window. This will prompt a toolbar to appear. This option is in the "Organize" section of the toolbar. Clicking Rename will cause the Excel file's name to become highlighted. Replace whatever comes after the period at the end of the file name with xlsx and then press ↵ Enter.  For example, if the document was named "Spreadsheet1.docx", you would change it to "Spreadsheet1.xlsx". If the file extension already is "xlsx", try using "xls" or "html". This will confirm your changes and change the file extension. Double-click the file to open it. If the file opens in Excel (or, if you selected "html" as the extension, a web browser), your file has successfully been recovered.  If you chose the "html" extension, you can convert the webpage into an Excel document by dragging the html file onto the Excel icon and then saving the file that opens as a new "xlsx" file. If the file still won't open, proceed to the next Windows method.

How would you rephrase that briefly using Vietnamese?
Bạn cần hiểu tại sao loại tập tin lại quan trọng. Mở Start. Mở File Explorer. Nhấp vào thẻ View (Chế độ xem). Tích vào ô "File name extensions" (Phần mở rộng tên tập tin). Chọn tập tin Excel. Nhấp vào Home (Trang chủ). Nhấp vào Rename (Đổi tên). Đổi loại tập tin. Nhấp vào Yes khi được hỏi. Thử mở tập tin.