1 Jan 96

Windows 95

If NT is already installed on a system, Windows 95 will create its own directory and install itself in the NT Boot Menu. If Windows 95 is installed with either OS/2 or Linux, it can be treated as just a different version of DOS.

However, Windows 95 is designed to replace older versions of DOS and Windows. It can run most old DOS and Windows programs. If users fall back on the old systems, then Microsoft has missed its objective. So there is no good way to run both Windows 95 and Plain Old DOS on the same system.

Windows 95 provides no menu system. It installs on the C: drive in the same way that DOS did. Its boot sector is written by the same "SYS C:" command. Its hidden files have a different name from those of DOS, so the two systems can coexist on the same disk, but this is not an easy design to carry off.

Windows 95 and Windows NT

Normally when an operating system is installed on a disk, it writes a new boot sector record. However, Windows 95 defers to Windows NT when it discovers that NT is already installed on the system. When it detects the NT system files, Windows 95 installs itself in a different directory and its hidden files in the root directory of C:. However, it writes it boot sector record not into the real boot area, but rather into the C:\BOOTSECT.DOS file that the NT knows how to load.

As before, NT presents a default menu with three items. The first two select NT itself, the third selects "DOS". When the last option is selected, NT loads the BOOTSECT.DOS program. Now, this program loads Windows 95.

Curiously enough, the simplest way to switch between an old DOS system and a new Windows 95 system is to have a copy of NT on the system. Simply make a copy of BOOTSECT.DOS before and after Windows 95 is installed in its own directory. Then by switching the two versions of that dataset, it is possible to select either operating system.

Also note that Windows 95 renames the DOS CONFIG.SYS to be CONFIG.DOS and the old AUTOEXEC.BAT becomes AUTOEXEC.DOS. These files have to be renamed back (and the Windows 95 version must be saved) when switching systems.

Windows 95 and OS/2 Dual Boot

When OS/2 is installed on the C: drive, it establishes a "Dual Boot" configuration. The old DOS boot sector record is copied to C:\OS2\SYSTEM along with the DOS versions of CONFIG.SYS and AUTOEXEC.BAT. The OS/2 "boot /dos" command copies these files back to C:\ and saves the OS/2 versions of these files.

The Microsoft documentation for Windows 95 tells the Dual Boot user to first use the "boot /dos" command to copy the old DOS files into the root. Windows 95 then installs normally, replacing the old boot sector. After it has been installed, the "boot /os2" command saves the new Windows 95 file into the C:\OS2\SYSTEM directory before restoring the OS/2 system files.

If you want to support OS/2, Windows 95, and an old PC DOS system, then the best trick is to make a backup copy of the old PC DOS files while they are in the C:\OS2\SYSTEM subdirectory while running OS/2 before installing Windows 95:

1. Before installing Windows 95, boot OS/2 (thus saving the old DOS files in the \OS2\SYSTEM directory. Now while OS/2 is running, copy the three files to another subdirectory.
   
   
2. To install Windows 95, "boot /dos" to install the old DOS files in the root and bring up the old DOS system. During installation, Windows 95 replaces or renames the old DOS system files.
   
   
3. After Windows 95 is installed, it is still possible to issue the "boot /os2" command to copy switch systems. Now, however, the Windows 95 boot sector, CONFIG, and AUTOEXEC will be copied to the \OS2\SYSTEM directory when the OS2 system files are moved to the root.
   
   
4. Now save a copy of this second set of Windows 95 "DOS" files. You now have a set of system files that corresponds to the old DOS system and a set for Windows 95.
   
   
5. While running OS/2 it is now possible to copy either the real DOS or Windows 95 files into the \OS2\SYSTEM directory before running the "boot /dos" command. The set of files chosen determines which system files end up in C:\ and therefore which operating system starts up. With this strategy is is possible to boot either system, but it is necessary to go back to OS/2 before switching between PC DOS and Windows 95.

Windows 95 and PC DOS

It is possible to get Windows 95 to boot the old DOS operating system. There is a parameter in a hidden file in the root that is set to enable this feature. Then, just as Windows 95 begins to load, you have a one second period to hit the F4 key to boot old DOS. This is not a workable arrangement.

The simplest way to keep a DOS Boot capability is to build separate boot diskettes. While running DOS, format a floppy with the command "format a: /s". The "/s" puts a boot sector, copy of COMMAND.COM, and copy of the two hidden operating system files on the floppy. Then copy over CONFIG.SYS and AUTOEXEC.BAT from the C: drive.

The statements in CONFIG and AUTOEXEC should explicitly load all device driver and other programs from the C: drive. The first statement of AUTOEXEC should probably be a simple

        c:

to make C: the current drive. AUTOEXEC should also have a statement of the form:

        set COMSPEC=C:\DOS\COMMAND.COM

Once DOS has been loaded, the system will stop using the floppy drive and will switch over to the copy of DOS on C. Other floppies can be loaded as needed. Booting DOS off a floppy is a bit slower than booting off a hard drive, but it is much simpler and more reliable than the F4 method.

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Copyright 1995 PC Lube and Tune -- Das Boot -- H. Gilbert

This document generated by SpHyDir, another fine product of PC Lube and Tune.