The disk partition hiding option is useful if you are running multiple operating systems at the same time and you are not running a boot manager.

For example, if you are running Windows NT from a FAT partition, and you boot Windows 98 from another partition, Windows 98 will see the partition from which Windows NT is running and incorrectly attempt to "repair" the file system containing NT.

Boot managers circumvent this problem by changing the partition types of all bootable partitions, other than the partition currently booted. The types are left as an unknown file system, so that they will be ignored by the currently booted partition. Using the disk partition hiding feature will do the same thing.

When this option is enabled, only the partitions for which the virtual machine has Read Write access are visible. The other partitions are changed to an unknown type. In addition, all writes to the Master Boot Record (MBR) where this information is recorded are intercepted. This allows multiple operating systems to run from the same disk but with different views of the same partitions.

Because of this feature, however, a boot manager program run inside a virtual machine with disk partition hiding enabled will not perform properly. If you wish to install and/or use a boot manager program in a virtual machine, then the disk partition hiding option should be turned off.

Partitions used by the guest operating system should be hidden from the host operating system. On the Windows NT host, the partitions can be unmapped using the Disk Administrator tool (described in this tech note). For the Linux host, be sure these partitions are not mounted.