Hi Farv,
First let me stress, that I haven't tried this myself. I found this procedure in a german mac forum and people reported that it worked for them. The way to go is to partition the drive on the Mac, and to create one HFS+ partition (that is the OS X file system) and one FAT32 partition for Windows. Then you connect it to your Windows pc and convert the FAT32 partition to NTFS (Windows XP preferred format). You will need to use the terminal to do so.
Before you type anything, be sure to read the full text.
To create one FAT32 partition with 30GB capacity named "WIN" and one HFS+ partition with 20GB capacity named "MAC", you would type the following into the terminal:
diskutil partitionDisk disk1 2 MBRFormat MS-DOS WIN 30G HFS+ MAC 20G
and hit return
The volume number disk1 has to be replaced by the one used by your Mac.To find the right number type the following in the terminal, first with your external hd disconnected, and then with your external drive connected:
ls -la /dev/rdisk?
Without your external volume you will get something like this:
PowerBook:~ ebbi$ ls -al /dev/rdisk?
crw-r----- 1 root operator 14, 0 28 Sep 20:14 /dev/rdisk0
With your external drive connected it will look similiar to this:
PowerBook:~ ebbi$ ls -al /dev/rdisk?
crw-r----- 1 root operator 14, 0 28 Sep 20:14 /dev/rdisk0
crw-r----- 1 ebbi operator 14, 4 28 Sep 20:48 /dev/rdisk1
In short, the new number you get, is the right number to use.
Beware: If you use the wrong number, eg. the drive number representing your internal HD, you will completely erase it and
loose all your data.
When the formatting has run its course, disconnect the drive and connect it to your windows machine and convert the FAT32 partition named "WIN" to NTFS.
-Petra
Dual G5 1.8, Alu PowerBooks Mac OS X (10.3.9)