Solution:

1) Click the 'Start' button to display the 'Start' menu.
2) Select 'Find' and select 'Files or Folders...'. (The 'Find: All Files' dialog box appears.)
3) Select the root directory to search in from the 'Look in' drop-down list box ( typically C:\).
4) Type MSDOS.SYS in the 'Named' box.
'Named' box
5) Click 'Find Now'.
6) Right-click on the file named Msdos.sys in the find results window. (A pop-up menu appears.)
7) To copy Msdos.sys to a diskette to make a backup:

a) Select 'Send To' from the pop-up menu.
b) Select '3-1/2 Floppy A:' (or other drive listed for the floppy drive).
'Send to'

8) Right-click on the Msdos.sys file. (A pop-up menu appears.)
9) Select 'Properties...' from the pop-up menu. (The 'Msdos.sys Properties' dialog box appears.)
'Properties' from pop-up
10) Click the 'General' tab.
11) Clear the 'Read-only', 'Hidden', and 'Archive' check boxes.
NOTE: This removes the Msdos.sys default attributes and enables the file to be edited.
Remove attributes
12) Click 'OK'.
13) Select the Msdos.sys file from the 'Find' window.
NOTE: The find results window may contain multiple files named MSDOS. The correct file is named Msdos.sys and is a system file.
14) Select the 'File' menu and select 'Open With...'. (The 'Open With' dialog box appears.)
15) Select 'WordPad' from the list box, and click 'OK'.. (The Msdos.sys file opens in WordPad.)
Open with 'WordPad'
16) Type the following in the [Options] section:
BootGUI=0
17) Select the 'File' menu and select 'Save As...'.
18) Select 'MSDOS.SYS' and answer 'Yes' to replace.
19) Reboot the computer to start in MS-DOS mode. (The computer starts in MS-DOS mode.)