If the workstation is booted from a DOS diskette in order to perform the DOS application install, the installation is restricted to those logical drives that have been formatted as FAT. This is because logical HPFS drives cannot be accessed in a native DOS environment.
When the system is booted with DOS 5, HPFS drives are not assigned drive letters and are invisible to the user. If DOS 4.01 with CSD UR35284 is used to perform the boot, drive letters will be assigned to all drives, whether HPFS or FAT. However, you cannot access the files on the HPFS drives. With earlier versions of DOS, even FAT drives that lie beyond the first HPFS drive will not be assigned drive letters.
Some installation programs store directory information into control files that are used at run time. For example, WordPerfect** 5.1 records the path to its subdirectories. On a hard disk with both FAT and HPFS logical drives, this can cause the installation program run in native DOS to record drive assignments that are wrong when the application is started from a virtual DOS machine.
Consider the following example of a hard disk setup for dual boot or with Boot Manager:
Table "Drive Letter Assignment"
Note that FAT drive in the extended partition appears as drive E: to the OS/2 Version 2.0 virtual DOS machine, but appears as drive D: when booted under DOS. Consequently, if the DOS application is installed on that partition when the system was booted under DOS, the drive letter it records in its control files will be D:. When the system is rebooted under OS/2 V2.0 and the application is run from a virtual DOS machine, the application will be looking to drive D:, which under OS/2 V2.0 is assigned to the HPFS drive of the extended partition. This will cause the application to miss the information it is seeking.
The user may be able to change the control file information and correct the error through the application. However, if the system is booted from DOS and the application is started, it will again be looking for the wrong drive.
In order to avoid this confusion we recommend that HPFS logical drives be placed last. In the above example, the FAT and HPFS logical drives in the extended partition should be transposed. This will allow the drive letters for the FAT partitions to be the same regardless of whether the workstation is booted from DOS or OS/2 Version 2.0.
More details on hard disk management can be found in Chapter 4 of the OS/2 2.0 Installation Guide.