External Drive "unable to be modified" with Mac

Question

Hi,
I've just begun playing around with my laptop, but am running into problems while moving things around and off of my external hard drive.
Before my Mac that I just got today, I had a Gateway PC laptop that I used my external hard drive with. On the Mac, whenever I try to move a file to a new folder it says that it cannot be moved because the drive cannot be modified. Also, I can't create new folders or even delete things.
I think it has something to do with the formatting, but is there anything I can do that will NOT erase what I have on the hard drive? I have 200+ gigs of data on this drive and no where to temporarily place it while I reformat the drive.
Also, if I do have to reformat the drive, is there a format that works both with Macs and Windows, so I can still use it on friends' and parents' computers.
Message was edited by: Rachel Whitfield
Message was edited by: Rachel Whitfield

Answer 1

Rachel,
Disk Utility is in your "Utilities" folder (of course). Here's how we do this:
/Applications/Utilities/Disk Utility
Let's cover a few terms while we're at it... Disk Utility is rather like iTunes in the way it looks (in fact, most everything "Mac" has a lot of features similar to those in iTunes). The list at the left side of the Disk Utility window (as in iTunes) is called the "source list." In the case of DU, this list shows "devices" and "volumes" at the top. Below those would be shown recent "disk images" that DU may have created or handled (you won't have any, and "disk images" are something you won't encounter for at least a few hours ).
A "device" is something physical, like your Superdrive or internal hard drive, and a "volume" is a logical "container" for files that is created on a given device. Think of it like the trunk of your car (the device), and the organizer you place in that trunk (a volume). DU shows volumes indented below the device that contains them. Since a volume is a logical framework (we call it a "file system") that holds your files, it is actually written to the device.
Windows uses specific "logical frameworks" (NTFS, FAT-32), and Mac OS uses a somewhat different one (HFS+). The Mac OS can, however, read any of the Windows formats ('cause Macs are more better, as you've already found), and DU knows how to write those FAT-32 logical frameworks.
OK, moving on... DU does many things. It can format (erase) volumes, changing them while it's at it if desired, but it can also format or partition a device. There's a bit of a difference between the two, sometimes. For example, you can "zero" either a device or a volume (which means to write continuous zeroes to the entire volume or device, in addition to simply giving it a new framework). One either a device or a volume, this is something you would do to completely destroy whatever data is on the device/volume. If you do it with a device, however, you get the additional benefit of "mapping out" any bad blocks (like dead spots) on the drive. This comes in handy if you ever find you're having problems with your drive.
Another difference between devices and volumes is that devices can be "partitioned". This is when you create multiple volumes on a single device. These separate volumes would appear on the Desktop of your Mac as individual drives, but they all reside on the one device. And of course, they can be of different formats (on my Desktop, I currently have my HFS+ Mac startup disk, and another NTFS disk for Bootcamp, both of them on my internal hard drive).
DU also repairs (or attempts to) errors that might occur in that logical framework we've already covered. These happen for various reasons, most frequently if we have an improper shutdown (such as a power loss). When this happens, we can lose important data. DU attempts to locate the problem, then fix it.
Finally, Disk Utility is what we use to create and manage "disk images". These are single files that act as "virtual disks," and can be "mounted" and "ejected" just like real disks. This is something that you will encounter soon, I'm sure, but don't need to worry about right yet.
I'll continue in another post (yeeesh, am I long-winded sometimes)...