[NTLUG:Discuss] Humpty Dumpty Syndrome: split and cat on a 5 gig file

[Lenrek Xunil]

I'm doing some pro bono work at my brother's church.

I needed to transfer a 5 gig backup file over a wireless network, so I
split it into 10 files.  I used the Gentoo installation CD-ROM, which
gives you a command line when you boot up.

Transferring the whole file was difficult because of interruptions
(windows update trying to reboot, norton live update trying to reboot,
acrobat reader trying to reboot as I was browsing the web, me getting
bored and doing another task that forced me to reboot)...  Thinking
now of the trouble it has caused me,  I would have taken my router/hub
and cables... but it's too late now.  Also, when I used the tar
command to backup the whole hard drive to another hard drive, to
include the 5 gig file, it gave me trouble when it got to that file
(eventually I just used "dd", but this is another topic).

Anyway, as a test run, I copied the files to a second hard drive and
tried to put them back together using a script:

#!/bin/bash
cat xab >> xaa
cat xac >> xaa
etc...

When it got to xai and xaj, it put out an error message for each
saying something like "file limit exceeded".  Now I know it was not
the hard drive, because it was a 40 gig hard drive that was mostly
empty.  This second hard drive, by the way, was partitioned to 30 gigs
using linux fdisk ("c" filesystem) and formatted as fat32 using
Windows XP.

So why can't I put the file back together again?  Is it that the cat
command can only handle so much?  Is it the formatting?  Please help. 
Thank you.

David