File extensions in Windows are hidden by default and are typically not something you have to worry about. When you need to recover a drawing from a backup (BAK) or autosave (SV$) drawing file, you need to change the file’s extension to DWG.
- Do one of the following:
- Windows 7: On the Windows Start menu, click Run.
- Windows 8: On the Windows Start screen, right-click (or use the swipe up gesture from the bottom edge of the screen) and click All Apps. Scroll to the Windows System section and click Run.
- Windows 8.1: On the Windows Start screen, click the All Apps button located near the lower-left corner of the screen (or use the swipe up gesture from the bottom edge of the screen). Scroll to the Windows System section and click Run.
- In the Run dialog box, Open text box, enter control folders and then click OK.
- In the Folder Options dialog box, View tab, clear the Hide Extensions for Known File Types option under the Advanced Settings group.
- Click OK.