USB drive error -- not enough free disk space


Mar 29, 2011
Hoping to get some help from you folks who clearly know much more than I do.

I'm trying to copy a large MS Outlook PST file from my work computer to a flash drive (drive: and am getting an error message saying I don't have enough free disk space.

The drive is 8 gigs, I've got various files on there that take up ~2+ gigs, and about 5.7 gigs of space remaining. The PST file is ~5.0 gigs and has already been compressed down from ~10 gigs.

Can anyone help me out? Seems like I've got plenty of free disk space to do this.

Conversely, if this approach won't work, can I buy a cable of some sort that will allow me to connect two computers and transfer the file from my work PC to my home Mac?

This probably isn't the issue, but what filesystem is the USB drive formatted with? There are file size limits for various filesystems.

For Fat32, 4 GB.
For Fat16, 2GB.
For NTFS, it's not going to be the source of your problem.

I just put my USB key in this machine, and the file format is FAT32. No files over 4 GB for me.

As to the final question, the most common such cable is a network cable; can you copy the file over your home network?

Umm, that's 4 gigs, but "No."

However: Back in the days when we carried data around on flexible pieces of plastic inside fiber sleeves, the size limit of the medium was about 1.44 Megabytes. Not Gigabytes, like your flash drive, but Megabytes. These fragile, primitive devices were called "Floppy Disks," although if one was floppy it was probably too damaged to use.

To transfer files larger than this limit, primitive man first developed compression software. To transfer files whose compressed size was larger than this limit, a great programmer named Ugh (I don't know why I'm doing this stupid olden-days cave-man riff; please excuse me) came up with the "spanned file." The compressed file was broken into 1.44 MB chunks, which could then be re-assembled by the decompression software at the receiving side.

So either reformat your USB key with the NTFS filesystem, or re-compress your mail file but find the settings in your compression software to break it into multiple files of less than 4 GB each. How to do this depends on which software and which version of it you are using.

Edit: Now that I think about it, 1.44 MB floppies are fourth generation or so. I have some 360KB 5.25" floppies around somewhere, although my drive requires a floppy controller, and those don't seem to exist anymore. The 8" floppy was in use at about 180 KB in 1972, if I can believe what I read on Wikipedia.

And the "fiber sleeves" were for the 5.25" floppies; 3.5" floppies have rigid cases. Old Grogg here is getting mixed up about his earlier days.

Edit: I'm going to go take my nap. I originally wrote "NFS filesystem" instead of "NTFS filesystem." NFS filesystems are for mounting disks on remote Unix hosts.


Jul 14, 2006
You can use a file splitter program to split the file into 4Gig chunks so that it fits onto your flash drive. Or if you have them already installed Winzip or Winrar will do the job as well.