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| Troubleshooting CD-ROM Drives | Drive Not
The CD-ROM drive cannot be recognized or seen by the system, or the CD-ROM driver hangs
or says it cannot find the CD-ROM when it loads
Explanation: You cannot access the CD-ROM. It is not being recognized by the system
and so is not usable. This usually manifests itself as an error message or lockup produced
by a CD-ROM driver at boot time, or getting an "Invalid drive specification
error" trying to reference the drive.
Diagnosis: There are a wide variety of causes for a CD-ROM drive that does not
register with the system. Most fall into the usual two categories: incorrect
configuration, and hardware problems or incompatibility.
Recommendation: You may find that the problem is actually more than one of the
following, but try them one at a time first:
- Check the power to the CD-ROM drive first. See if the activity LED works. Try to open
the tray. If the tray doesn't open the drive does not have power; check the plug
connection to the drive inside the case. If it doesn't work, try another one. If you can't
get power to the drive, it is most likely dead and needs to be repaired or replaced. If
you have intermittent power problems or problems with other devices as well, the power
supply could be a problem.
- If the CD-ROM works in Windows 95 but does not work when you "restart in MS-DOS
mode", then you have a relatively simple system file configuration problem. See here for a solution.
- If you have recently installed this drive, or have worked in the system case recently, consult this troubleshooting list of common problems.
- If you have another system that you can try the drive in, it is a good idea to connect
it to the other PC and see if it will be detected there. Bear in mind that moving the
drive to a new PC can introduce other variables that might confuse the issue, but I have
seen this be a very effective way to isolate the trouble to either the CD-ROM drive or the
PC it is installed into. Similarly, if you try another identical (or even just similar)
CD-ROM in place of the one not working, that can tell you if the problem is the drive or
the drive interface.
- If you have a DOS CD-ROM driver in your CONFIG.SYS file, check to make sure that it has
the correct parameters. If you recently moved the drive to a different IDE channel or
changed it from master to slave or vice-versa, you may need to change the command that
invokes the driver. Look here for more.
- On some systems, loading the CD-ROM driver in CONFIG.SYS will cause conflicts with other
IDE devices. This will cause the CD-ROM drive not to be found within Windows 95. If this
happens, try temporarily removing the CD-ROM driver command from CONFIG.SYS and see if
Windows 95 now sees the device. If it does, you should leave the line out of CONFIG.SYS
permanently. This will mean you cannot access the CD-ROM under DOS any more, but there is
a workaround: creating a custom boot profile for DOS programs. See here for more.
- If you are using the drive in DOS (or Windows 3.x, or Windows 95 MS-DOS mode), you must
have a CD-ROM driver in your CONFIG.SYS, and you must run MSCDEX to create the drive
letter for the drive (usually it is in AUTOEXEC.BAT; sometimes it is in DOSSTART.BAT in
the Windows directory, in Windows 95). You must make sure that you use the right driver
for your drive (it should come with an install program on a floppy that will take care of
- If using a DOS driver and MSCDEX, and you are encountering errors with MSCDEX, refer to this section.
- If you are connecting an older CD-ROM drive, especially one that is 2X speed or slower,
there is a good chance that it uses a proprietary
interface, not standard ATAPI/IDE.
These drives use a connector and cable that looks much like standard IDE, so it is easy to
confuse them. In most cases these will work off the special ports on some sound cards
(since they were originally sold as part of multimedia kits) but in some cases they
require special dedicated controllers. Make sure to read your product documentation.
(There are some real IDE/ATAPI 2X drives, by the way.)
- If the drive is SCSI, you need to
check all of the various parts of the SCSI chain. The SCSI host adapter (controller) must
be checked to ensure that it is working properly. The CD-ROM drive and all other devices
on the SCSI chain must have a different device ID. The termination must be set up
correctly. See here for more details on
- If the drive is on an IDE channel with another drive (hard disk or CD-ROM), then you
should try the disk by itself on the channel to eliminate the possibility of conflict. You
may need to change the jumpers on the drive to do this, but you definitely need to
try the drive without the complicating factor of another device on the channel. If the
disk works by itself but not when set up with another drive, you may have a master/slave
conflict; see this section in the hard disk area
for ideas on fixing these problems (the general guidelines are the same for CD-ROM
drives.) Note that some drives may not work by themselves on a channel so don't assume
that this means the drive is bad.
- Beware of some CD-ROMs that will not work by themselves on an IDE channel if bus mastering drivers have been installed for the hard
- Some CD-ROMs will only work on an IDE channel by themselves if they are jumpered as
master (this is the "correct" way to jumper them, but some drives will work as
solo slaves on a channel, others will not.)
- Make sure that the CD-ROM drive is configured properly. The jumpers should be set
correctly. The ribbon cable should be inserted properly and pin 1 on the drive should be
matched up with pin 1 on the interface controller or motherboard.
- If you had a master and a slave drive on the IDE channel and removed one of the two
drives, the one that remains may need to be rejumpered. Similarly, if you add another
drive to the channel the first one there may need to be changed, even if you are adding a
slave to an existing drive. Some hard disks--for example those manufactured by Western
Digital--use different jumpers for when they are a master with a slave drive present vs.
when they are alone on a channel.
- Make sure that the IDE controller is enabled if you are using an ATAPI/IDE drive; on
modern systems the IDE controllers are enabled or disabled using BIOS settings. It is common for
the secondary controller to be disabled; if you are adding a CD-ROM to the secondary
channel you will need to enable the channel.
- Some hard disks do not like having CD-ROMs attached to them as slaves, in general. You
should try the CD-ROM on a different channel (again, isolate the problem by seeing if the
drive works by itself on a channel, bearing in mind that some won't).
- If the drive isn't recognized by itself on one channel, try another and see if the
problem is fixed. If so, this implies that the original IDE channel is misconfigured in
some way. There may be a resource conflict or other problem with the channel. This is
especially true if you have the unit on a tertiary controller, for example one found on a
- Tertiary IDE controllers, such as those found on sound cards, often do not work with bus
mastering IDE drivers installed. See here for more on
bus mastering driver problems.
- An IDE cable that is too long can cause permanent or intermittent problems with drives.
Make sure the cable is not longer than the nominal 18" limit. Try an even shorter
cable if problems ensue.
- If another similar CD-ROM drive is available, try replacing the CD-ROM drive with this
one (you can just leave it loose and move the power and interface cables while testing, if
you are careful). You may need to change the driver that is loaded in CONFIG.SYS if you
use a different manufacturer's drive. See if the problem goes away. If it does the drive
may be bad; otherwise the interface is implicated.
- Another test to isolate a problem to the drive or the interface is to try a hard disk in
the position where the CD-ROM drive was. If the hard drive works but the CD-ROM does not
then that tells you that either the CD-ROM is bad or there is a compatibility problem
between the interface and the CD-ROM drive.
- Watch out for 32-bit disk access being enabled under Windows 3.x. This may cause
problems with CD-ROM drives on the ATAPI/IDE interface.
- Systems with dynamic drive overlays
installed to allow use of larger hard disks may not be too impressed if you put a CD-ROM
on the same channel as the hard disk. I have seen systems refuse to boot under these
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