Zip Drives do write-caching by default, you can't turn it off.
These errors in the event log are fairly common w/ zip drives,
don't worry too much about them.
if you install the IOMegaWare drivers you'll get more right-click options,
and an IOMega tab in the properties dialog, but it is not truely required;
I like to have it installed - biggest benefit is the disk gets ejected at
shutdown if you forget to do it, instead of being stuck in there until
next powerup. [it installs 2 processes that run at startup].
you do not need the "Active Disk" thingee that it installs, reboot and go
into Add/Remove and remove Active Disk. [IoMega App Services you do need
tho, don't remove it].
Having the IOMegaWare doesn't seem to reduce the frequency of these error
log entries tho. I see them occasionally still; it's often logged well
after I've ejected the disk (minutes); I suspect perhaps explorer is
trying to refreash something and is unaware that the disk is gone? I'm not
sure... I usually do use the right-click eject (not the physical button),
so it should know the disk has been removed. whatever...
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REAL errors w/ Zip disks (disks, not the drive) are usually preceded by a
noticable CLICK sound comming from the drive - this is the drive
recalibrating the head position servo upon a disk write/verify operation.
If you hear this retract-click-reseek noise (usually two ro three times in
a row) then the DISK is probably getting old; when possible do a LONG
format on the disk (you'll need the iomegaware installed) to redo the
surface scan, and then check the disk's life expectancy in the properties
dialog - retire the disk if it's getting bad.
The above is not the notorious "Click of Death" that plauged older zip
drives; that problem has been fixed for years.
Good Luck