To change the default drive in Excel, first open the File tab. Then click Options. In the left pane of the Excel Options dialog box, click Advanced. Under General, in the Default file location box, type the path of the folder that you want to use as your default drive, and then click OK.

If you want to use a different drive as your default drive, you can also do so by opening the File tab, clicking Options, and then selecting the new drive from the Default file location drop-down list.