Extra Characters in the Msdos.sys File
The Msdos.sys file also contains a section that contains seemingly useless information. This information is necessary to support programs that expect the Msdos.sys file to be at least 1,024 bytes in length. For example, if an antivirus program detects that the Msdos.sys file is less than 1,024 bytes, it may assume that the Msdos.sys file is infected with a virus. If you delete the Msdos.sys file your computer will not start.
The following statement, followed by a series of "X"s, appears in the Msdos.sys file:
;The following lines are required for compatibility with other programs.
;Do not remove them (Msdos.sys needs to be > 1024 bytes).
Because each line begins with a semicolon (;), the lines are not read by Windows.