Hidden System Files and MS-DOS 5 and Later Upgrade

Article translations Article translations
Article ID: 74589 - View products that this article applies to.
This article was previously published under Q74589
This article has been archived. It is offered "as is" and will no longer be updated.
Expand all | Collapse all


The Microsoft MS-DOS Upgrade Setup copies the hidden system files IO.SYS and MSDOS.SYS to the front of the root directory in the boot drive. If the previous version of DOS had files called IO.SYS and MSDOS.SYS created by Microsoft, those files will be deleted.

If the previous version of DOS has hidden system files by other names or that were not created by Microsoft, they are moved to the first available space in the root directory of the bootable hard drive. These files can then be deleted after resetting the file attributes.

The following command will turn off the system file attribute, the hidden file attribute, and the read-only file attribute of a file named IBMBIO.COM.
attrib -s -h -r ibmbio.com
These files can also be deleted using MS-DOS Shell.


Article ID: 74589 - Last Review: October 7, 2013 - Revision: 2.1
  • Microsoft MS-DOS 5.0 Standard Edition
  • Microsoft MS-DOS 5.0a
  • Microsoft MS-DOS 6.0 Standard Edition
  • Microsoft MS-DOS 6.2 Standard Edition
  • Microsoft MS-DOS 6.21 Standard Edition
  • Microsoft MS-DOS 6.22 Standard Edition
kbnosurvey kbarchive KB74589

Give Feedback


Contact us for more help

Contact us for more help
Connect with Answer Desk for expert help.
Get more support from smallbusiness.support.microsoft.com