online help

Use of all Windows 9x versions to perform install or update.
Windows 3.x — Windows 95 (95, 95A, 95B, 95C, OSR1, OSR2, OSR2.1, OSR2.5)
Windows 3.x — Windows 98
Windows 95 (all) — Windows 95 (all)
empty system — Windows 9x (with usage of Update release)

Method One
Upgrading an older version of Windows (3.x or 95) to OSR2
I. Copy the Win95 source files from the Win95 directory on the OSR2 CD to a hard drive.
II.Create and save an MSBATCH.INF file in the same directory where you copied the Win95 files to.
The file must contain the following lines:
Follow the last line by a carriage return otherwise you'll get a Data Control Corrupt error. The file MUST be called MSBATCH.INF and MUST exist in the same directory as the Win95 source files. You will still be able to specify another customized batch file on the SETUP command line or you can add any other custom information to this MSBATCH.INF

Method Two
Rename the file "WIN.COM" in the C:\WINDOWS directory. Then run setup on the OSR2 CD from the DOS prompt. This will upgrade your current version of Win95 to OSR2.
Tip: Remove all entries from C:\windows\start menu\programs\startup before you upgrade. Of course, you will need your DOS CDROM drivers properly configured to read from your CDROM under DOS. Do not attempt this unless you are comfortable mucking around with system files. Finally, once you get OSR2 setup running, and you get to the screen where you specify which directory to install to, the default will not be C:\WINDOWS\. Manually change the install directory to C:\WINDOWS\ (or wherever your existing version of Win95 is) to upgrade your existing installation.

Method Three
This method can only be used if you have your OEM number from you certificate of authenticity on your manual (format: XXXXX-OEM-XXXXXXX-XXXXX): you will be prompted for this during installation.
I. Start up the OSR2 setup as normal, from within Windows95.
II. When you are presented with the License Agreement dialog box, stop. Don't click anything yet. Resist the urge to click "Next." Just stop!
III. Open Start Menu (CNTRL + ESC) and click "Run." Type "Notepad" and click "OK".
IV.Open the file "setuppp.inf" in the directory WININST0.400. This directory and its associated files were created by the OSR2 setup program.
V. Find the line in the file with the text "[data]". Add the following line after it: "OEMUP=1". The text should look as follows: [data] OEMUP=1
VI. Save the file and exit Notepad.
VII.Switch back to the OSR2 setup (using Alt+Tab) and continue with OSR2 installation.

Method Four
This method changes OSR2 to an upgrade version, and does not require the input of any CD Keys or numbers from the Certificate of Authenticity.
I. Make a temp directory on a hard drive - the standard directory for this is C:\WINDOWS\OPTIONS\CABS.
II. Copy the Win95 directory from the CD to the new directory on your hard drive. From here, we work with the files on your hard drive.
III. Extract from PRECOPY2.CAB the file called SETUPPP.INF. Use extract.exe, or use the CAB file extraction tool PowerToy provided by Microsoft.
IV. Open LAYOUT.INF in a text editor. Search for the string "SETUPPP.INF".You should find: setuppp.inf=2,,4550 Change the 2 to a 0 to read: setuppp.inf=0,,4550
Save the changes. This prevents setup from extracting SETUPPP.INF from the CAB file during installation. Setup will instead use a SETUPPP.INF file we create in step 5.
V. Open SETUPPP.INF in a text editor. Search for "ProductType". You should find: ProductType=9 Change 9 to 1 to read: ProductType=1
Save the changes. This tells setup to upgrade the previous installation, and to not ask for a CD Key or Certificate number. Just leave SETUPPP.INF out in the directory with all the other setup files & cab files.
VI. Run SETUP from Windows95 off your hard drive. Installation will proceed as an upgrade. Make sure that you CHANGE the install location from C:\WINDOWS.000 to C:\WINDOWS.

ProductType=X in SETUPPP.INF

ProductType=1: Upgrades without asking for CD KEY (serial number)
ProductType=2: Asks for 10-digit CD KEY
ProductType=3: Forces a floppy install - doesn't work.
ProductType=4: Fails - Error - previous ops system installed.
ProductType=5: Works - asks for CD KEY, but won't take valid keys- can "ignore"
ProductType=6: Works OK (?) (?)
ProductType=7: Fails - Error - previous op system
ProductType=8: Fails - Error - previous op system
ProductType=9: OEM non upgrade version

WARNING: If you currently have set Windows 95 (release version) up to dual boot with Windows 3.1. or DOS, and you force OSR2 to "upgrade" in the manner described above, you will lose the ability to dual boot. That is, you will no longer be able to choose to boot to DOS or Windows3.x. Microsoft has removed this ability from OSR2. For more information on this, see Microsoft's Knowledge Base Article on the subject.

Method Five
There is a fifth method, courtesy Roberto Franco, however, this method is no better than the previous methods.

Method Six
Format your harddisk you wish Windows 9x to be installed on. Copy a file named NTLDR. on this partition. File length should be 0 byte. Windows9x Update version will accept this file as WindowsNT and therefore 'upgrade' to Windows9x.