Removing a partition created by a third-party disk-partitioning utility can
reduce the total usable space available on the hard disk drive. This
problem is most commonly experienced with, but is not limited to, the
• XT systems with hard disks that are larger than 20 megabytes (MB)
• Systems with hard disks that have more than 1024 cylinders
IMPORTANT: Microsoft cannot guarantee whether or not it is safe to remove a
third-party disk partition. If in doubt, contact the manufacturer of your
Some hard disk drives are not fully supported by the system BIOS. This
problem most commonly occurs when the disk uses more heads, cylinders, or
sectors per track than is supported by the standard IBM ROM BIOS protocol.
The IBM ROM BIOS protocol is limited to 1024 cylinders by 256 heads by 63
sectors per track. Using the standard of 512 bytes per sector, the drive
size is limited to 8064 MB (where 1 MB = 1024 x 1024 = 1,048,576 bytes) or
7.875 gigabytes (GB) (where 1 GB = 1024 MB).
This problem also occurs when the system doesn't support the exact
combination of heads, cylinders, and sectors per track that the disk uses.
As a result, special disk-partitioning utilities have been created that
will fully use the hard disks on such systems. Examples of these utilities
include the following:
• Disk Manager by OnTrack Software (DMDRVR.BIN, XBIOS.OVL)
• SpeedStor by Storage Dimensions (SSTOR.SYS, HARDRIVE.SYS)
• VFeature Deluxe by Golden Bow Systems (FIXT_DRV.SYS)
• InnerSpace by Priam Systems (EDVR.SYS)
• Everex by Everex Systems (EVDISK.SYS)
Once the partitioning utility has been used to recognize the entire drive,
removing the non-MS-DOS partition may result in the hard disk size
"shrinking" to what is actually supported by the system ROM BIOS. Returning
to full use of the drive usually requires reinstalling the partitioning
software. Contact your partitioning software manufacturer for more
The full hard disk drive can be used without the third-party partitioning
software if the system fully supports the hard disk drive. A hard disk
drive is generally considered fully supported if it has 1024 or fewer
cylinders and the system ROM BIOS was written to correctly recognize it.
Even if the hard disk drive has more then 1024 cylinders, the third-party
software may not be required if the drive has a translating controller card
to translate the real drive parameters to parameters that the ROM BIOS can
To determine whether the hard disk drive requires the third-party
partitioning utility, refer to the utility's documentation or manufacturer,
or possibly the hard disk drive's documentation or manufacturer.
The partitioning utilities included here are manufactured by vendors
independent of Microsoft; we make no warranty, implied or otherwise,
regarding these product's performance or reliability.