This article was previously published under Q149110
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When you use the SYS command to replace the Windows 95 system files onyour hard disk, the Msdos.sys file may not be replaced, or may be replacedwith an incomplete Msdos.sys file that contains only the text ";SYS."
If the existing Msdos.sys file on your hard disk is damaged and is notreplaced by the SYS command, or if the existing Msdos.sys file is replacedwith an incomplete Msdos.sys file, Windows 95 may boot only to a commandprompt the next time you start Windows 95. If the existing Msdos.sys fileis not damaged and is not replaced by the SYS command, no problems occur.
If the SYS command (Sys.com) included with Windows 95 determines thatthe existing Msdos.sys file is from MS-DOS version 6.22 or earlier, itreplaces the existing Msdos.sys file with an incomplete Msdos.sys filethat contains only the text ";SYS." If the SYS command is unable todetermine that the existing Msdos.sys file is from MS-DOS version 6.22or earlier, it assumes that the file is a valid Windows 95 Msdos.sys fileand does not replace it.
To work around this issue, manually rebuild the Msdos.sys file on yourhard disk so that it includes the location of your Windows folder and theWindows 95 system files. To do so, follow these steps:
Remove the system, hidden, and read-only attributes from the Msdos.sys file in the root folder of the boot drive. To do so, type the following command at the command prompt
attrib -s -h -r <drive>:\msdos.sys
where <drive> is the physical boot drive.
NOTE: If drive C is compressed and is currently mounted, the Msdos.sys file is located on the host drive for drive C. If drive C is not compressed or is not currently mounted, the Msdos.sys file is located on drive C.
Rename the Msdos.sys file using the following command
ren <drive>:\msdos.sys msdos.xxx
where <drive> is the physical boot drive.
Use any editor (such as Edit.com) to create a new Msdos.sys file that contains the following text
where <drive> is the drive containing the Windows folder, <windows> is the Windows folder, and <boot drive> is the physical boot drive. For example, if you installed Windows 95 on drive C in a folder named Windows and drive C is not compressed, the Msdos.sys file should contain the following lines:
NOTE: You can also add an [Options] section to the Msdos.sys file with additional settings to personalize the boot process. For information about the [Options] section, please see the following article in the Microsoft Knowledge Base:
When you use the SYS command to replace the Windows 95 system files onyour hard disk, the SYS command replaces the existing Msdos.sys file onlyif it determines that the file is from MS-DOS version 6.22 or earlier. Todetermine if the Msdos.sys file is from MS-DOS version 6.22 or earlier,the SYS command checks to see if the first byte in the file is 0x3Bh,0xE9h, or 0xEBh. These hexadecimal values indicate that the file is abinary file and that it is likely a valid Msdos.sys file.
This logic is intended to prevent the SYS command from replacing a validWindows 95 Msdos.sys file. However, when the SYS command replaces theexisting Msdos.sys file, it replaces the file with an Msdos.sys file thatcontains only the text ";SYS." Creating an Msdos.sys file without a[Paths] section is appropriate when you are replacing the Windows 95system files on a floppy disk, because the location of the Windows foldermay not be the same on the computer used to create the bootable floppydisk and the computer on which the floppy disk is used. Creating anMsdos.sys file without a [Paths] section is not appropriate when you arereplacing the system files on a hard disk, but the SYS command cannotdistinguish between a floppy disk and a hard disk.
If the first byte in the existing Msdos.sys file is not one of thehexadecimal values listed above, the SYS command assumes that the file isa valid Windows 95 Msdos.sys file and does not replace it. Therefore, ifthe existing Msdos.sys file is an ASCII text file, or if it is damaged(and the first character in the file does not happen to be one of thehexadecimal values listed above), the file is not replaced.