Welcome to the MacNN Forums.

Big Mac · 10:37 PM

I recently set up an external 500GB USB drive, which I partitioned into a large Mac volume for Time Machine and a small, 22GB MS-DOS (FAT32) volume for backing up the critical files on my Dell. I formatted the disk using Disk Utility (and diskutil) on my G5 running Leopard. My G5 sees both volumes properly, but alas XP only sees the disk as an unallocated chunk of space. My brother laughed at me for expecting Windows to run that well. I looked around the System Management utility in XP to see if I could figure anything out, but I didn't want to make any changes to the disk for fear of destroying my Mac volume. I installed MacDrive and it was able to see my HFSJ volume, but I wasn't able to get it to see the FAT volume. Now I realize I probably should have originally formatted the drive on my PC and then reformatted a partition to HFSJ on my G5, but since I didn't do that is there anything I can do without reformatting the disk completely to get XP to see the FAT volume?

nonhuman · Apr 5, 2008, 10:44 PM

When the PC sees the external drive as unformatted space, is that only the 22 GB FAT32 volume or the whole thing? I've definitely had to reformat partitions that bootcamp created before with whatever OS, but I've usually beena ble to do so without affecting my HFS+ partition(s).

Big Mac · Apr 5, 2008, 11:20 PM

It shows the whole drive as unallocated, unfortunately. When I had MacDrive installed it saw both the Mac volume and the "unallocated" 22GB, but I couldn't do anything with that space using the built-in Windows utility because MacDrive prevents Windows from dealing with a drive that it mounts; MacDrive itself only wanted to deal with the Mac volume and didn't see the FAT volume either.

hookem2oo7 · Apr 5, 2008, 11:22 PM

is the drive partitioned with the MBR partition table? if it's with APM or GUID, Windows XP won't see any partition, no matter the format

Big Mac · Apr 5, 2008, 11:27 PM

Really. Wow. Damn, that makes a whole lot of sense. I think I remember changing the partition scheme over from MBR because I didn't like thinking about it being in Windows format

. Can I change it back to MBR without destroying my data?

hookem2oo7 · Apr 5, 2008, 11:29 PM

only if you backup your data and restore if after repartitioning. When you change the partition format, all is lost.

Big Mac · Apr 5, 2008, 11:29 PM

Damn it, I thought that was the answer. TYVM, hookem.

hookem2oo7 · Apr 5, 2008, 11:33 PM

what you might try....i've done it before, but don't really remember the process...is to "repartition" your drive using one of the command line utils. you create a mbr partition table that windows can recognise while keeping the APM/GUID intact so OS X still knows how to access those partitions. I did it a couple of years ago trying to share a drive between an iBook G4 and a Windows PC. I just did some google searching and found what i needed to know. I basically used fdisk (i think) to make a MBR style partition table so Windows knew where the FAT partition started and stopped on the disk so it could access it.

Big Mac · Apr 5, 2008, 11:43 PM

Interesting. I just read this Apple doc that implies MBR formatted drives screw up Time Machine backups.

I have no idea how I'd go about creating an MBR without destroying the Mac partition map. If the procedure comes to your mind or you can direct me on the right path, please let me know. Otherwise I guess I'll just give up on backing up my Dell.