Are these other two computers Windows PCs?
If you so, you probably have the hard drive formatting using the NTFS file system. Macs are supposed to be able to read but NOT write to NTFS drives.
What does Disk Utility on the Mac say about this drive when it's plugged in?
My Filesystem is Mac OS Extended, and it says Case Sensitive also.
Heres everything Disk Utility will tell me. First aid fails every time
Here ya go, it doesn't look good 🙁 This was when I attempted to verify disk.
Verifying volume Time Machine Backups
Checking Journaled HFS Plus volume.
Detected a case-sensitive catalog.
Checking Extents Overflow file.
Checking Catalog file.
Checking multi-linked files.
Checking Catalog hierarchy.
Checking Extended Attributes file.
Invalid node structure
Volume check failed.
Error: Filesystem verify or repair failed.
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note: the last 3 lines ("invalid node structure" to the bottom) are all in red
Sorry to hear that because that is precisely the error I was experiencing. Your mileage may vary of course but if the lost data is that critical to you there is a good chance DiskWarrior can succeed in fixing it where fsck failed.
In my case it was a catastrophic write error caused when I inadvertently powered off my external while Time Machine was writing to it. 🙁
Good luck.
What brand model is it and have you checked the manufacturer's site for disk utilities that will perform a advanced diagnostic.
Can you format the drive?
Nope, the HD has been fine until I came back from my 3 week trip about 2 days ago. Until the day I left, I was using it daily to back up my machine. Yes the PCs are windows, but the disk doesn't even show up in disk utility when it is plugged in and turned on, nor does it appear on my desktop at all.
edit: read post #4
It is a 500GB IOmega drive, and after checking their website, I believe that I am out of luck. They offer data recovery, which is not what I am looking for.
I haven't tried yet, but I will now. Is this a good website to follow? http://www.kenstone.net/fcp_homepage/partitioning_tiger.html
I only want 1 partition on the external HD.
I read the whole post, but as I am not a computer guy I did not understand a lot of the stuff in the middle. So why reply?
I was using a firewire connection from computer to external hard drive that worked fine. Later after returning from a 3 week vacation my computer would no longer recognize the hard drive.
Eventually I tried connecting the hard drive with a USB cord. Now it works.
That's the extent of my advice, good luck.
I apologize, I have made some changes to my post to help clear up some issues.
another edit: I have tried erasing and formatting the disk using Disk Utility, except when I selected "Don't erase data", it said that an error occured and that the "resource is busy". When I tried "zero out data", it said there was an error and that it could not open the disk. This was when I tried to format the disk as Mac OS Extended (Journaled). Should I try something else?