Existing IDE drives on the host computer can be used as virtual machine disk drives. If an existing partition is empty, an operating system can be installed in the partition. If the host is a dual-boot or multi-boot system then bootable partitions on the host computer can also be booted within the virtual machine. VMware does not support using existing disk partitions on SCSI, RAID or network disk drives. More information about working with existing disk partitions is available on VMware web site's technical notes for Windows NT
It is generally not possible or advisable to try to run the host operating system again inside the virtual machine. Doing so may cause the host system to crash and possibly cause disk corruption if two operating systems attempt to concurrently use the same disk partitions.
When configuring an existing disk partition, you are given the option of enabling disk partition hiding. The Disk Partition Hiding option is useful if you are running multiple operating systems at the same time, and you are not running an advanced boot manager, such as PowerQuest's BootMagic or V Communication's System Commander. 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 that Windows NT is running from, and will attempt to repair that file system. This may damage your disk and/or cause your computer to crash.
Some advanced boot managers solve this problem by changing the partition type of all the partitions not needed by the operating system being booted to an "unknown" type. If you are not using an advanced boot manager, then selecting Disk Partition Hiding will do the same thing.
When this option is enabled, only the partitions for which the virtual machine has Read/Write access are visible to the guest operating system. The other partitions are changed to "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 on the same disk, but with different views of the same partitions.
Because of this feature, however, one of these advanced boot manager program run inside a virtual machine with Disk Partition Hiding enabled will not function properly. If you wish to use an advanced boot manager program, or install a new boot manager from within a virtual machine, then the Disk Partition Hiding option should be turned off.
A virtual machine can have at most four virtual IDE disk devices. If a host system has four disk drives then configuring all four disk drives in the virtual machine will not leave space for a virtual IDE CD-ROM drive. Even if the host computer has a SCSI CD-ROM, the drive still appears inside the virtual machine as an IDE device. If you have configured four IDE disks in a single virtual machine, you will be warned at the end of the disk configuration panels that you will not have room for a CD-ROM drive. At this point, you can either continue and configure your virtual machine without a CD-ROM, or you can use the Back button to return to the previous screens and remove one or more of the configured hard drives.
The Configuration Wizard always requires that the first IDE disk drive found be configured as virtual IDE drive 0:0