The Macintosh needs version 4.2 of the Iomega Driver to be able to communicate with the Zip drive. This means your Macintosh will only recognize a connected Zip drive if the 4.2 Iomega Driver is correctly installed on the system. (See Section 3.3, Loading the Driver, for detailed information.)
In addition to the Zip drive, version 4.2 of the Iomega Driver supports Iomega LaserSafe Plus and Floptical drives. It does not provide support for Iomega Bernoulli drives.
Versions between 3.0 and 4.0 of the Iomega Driver support Iomega Bernoulli drives but do not support Zip, Floptical, or LaserSafe Plus drives. The icon for this series of the Iomega Driver looks like this:
 
The 4.2 Iomega Driver is fully compatible with versions between 3.0 and 4.0, and you can use one of these earlier versions and the 4.2 Iomega Driver on your Macintosh at the same time without any conflicts.
Versions between 4.0 and 4.2
Versions between 4.0 and 4.2 of the Iomega Driver support Floptical and LaserSafe Plus drives, but do not support Zip drives. When you install the 4.2 version of the Iomega Driver using the Zip Install program, these earlier versions are no longer needed and will be automatically removed from the System Extensions folder.
When version 4.2 of the Iomega Driver is installed on your startup disk using the Zip Install program, it should load automatically each time you start your Macintosh. You can then use your Zip drive like any other disk drive on your system.
You can also load the 4.2 Driver temporarily by using the Iomega Guest program. This allows you to load the Driver without having to install it in the System Extensions folder. The Guest program is designed to make it easy to use your Zip drive temporarily on another Macintosh; however, if desired, you can routinely use Iomega Guest to load the Driver.
Whether the Driver loads as an extension during startup, or you use Iomega Guest to load the Driver, it provides the same support for your Zip drive (or Floptical or LaserSafe Plus drive). The only difference is that when using Iomega Guest to provide access to your Zip drive you must manually run the Guest program each time you start or restart the Macintosh. When the Driver is installed in the System Extensions folder, access to your Zip drive will be automatic as soon as your Macintosh completes startup (provided the Driver loads successfully).
Section 3.3.1
Loading the Driver Using Iomega Guest
In some situations, the best way to load the Driver is by running the Iomega Guest program. You will want to use Iomega Guest when:
• You want temporary access to the Zip drive on a Macintosh where the 4.2 Driver is not installed in the System Extensions folder.
• You are using Zip drive on a Macintosh with low memory (4MB RAM). To maximize memory resources, you can run Iomega Guest whenever you need access to your Zip drive (such as for a backup). When you are finished using your Zip drive, you can restart to free the memory used by the Iomega Driver. (The Iomega Driver requires less than 100KB.)
• You are troubleshooting hardware or software conflicts that are preventing access to the Zip drive. In this case, you can start the Macintosh with extensions turned off (by holding down the Shift key while starting) and then run Iomega Guest. Guest will inform you whether it loads successfully or is unable to find the Zip drive. (See Section 7, Solving Problems, for detailed troubleshooting procedures.)
For additional information on using Iomega Guest, refer to Iomega Guest Help which is located on the Install floppy for Macintosh.
Section 3.3.2
Loading the Driver as an Extension During Startup
When the Driver is installed in the System Extensions folder on your startup disk, you will see the Iomega Driver icon at the bottom of the screen when the Driver loads successfully during startup:
 
NOTE: You will see the icon during startup only if the Driver is installed in the startup disk System Extensions folder. If you start from a Zip disk, but do not have the Driver installed in the System Folder on the Zip disk, you will not see the icon. In this case, the Driver loads from a special startup area of the Zip disk.
You will see more than one icon during startup if there are multiple copies of the 4.2 Driver in the System Folder. Having extra copies of the 4.2 Driver present at startup is not a problem; however, you may want to delete the extra copies from your System Folder.
If the Driver is installed in the startup disk System Folder, but it is unable to load successfully during startup, you will see the no-load icon at the bottom of the screen:
 
The Driver may not load if:
• A supported Iomega drive (Zip, Floptical, or LaserSafe Plus) is not connected to the Macintosh or is not turned on before startup.
• Another version of the Iomega Driver higher than 4.0 is already loaded. (In this case, you will see a dialog box explaining why the Driver cannot load.)
• A third party driver (such as MultiDriver, HDT, or Drive7) is already loaded and trying to control the Zip drive.
If the Driver cannot load, you may be unable to use your Zip drive. If you see the no-load icon at startup, refer to Section 7.1 for problem-solving help.
You may encounter other problems caused by hardware or software conflicts. If you experience any of the following, refer to the referenced section for help:
• When you attempt to start the Mac, a disk icon with a flashing "?" appears on the screen. (See Section 7.3.)
• The Macintosh locks up during startup. (See Section 7.4.)
• The Zip disk does not eject when the disk icon is dragged to the Trash. (See Section 7.10.)
• You can't eject a Zip disk and you get a message saying the disk is being shared. (See Section 8.3.)
• Your Zip drive intermittently produces read/write errors. (See Section 7.11.)
