I have a 400 GB external Seagate USB drive, that was setup with FAT32 (When I have the chance, I'll convert it to NTFS).  It won't allow me to copy any more large (3-6 GB) mpeg2 files from my desktops 2 HDs.  I've only used about 120 GB on the USB drive.  I deleted some files and still couldn't add any more.  I did a full check disk of the USB drive with no errors.  There's no file sharing or networking on any drives.  I TURNED off SageTV software thinking that somehow it's locking on to the files.  I rebooted the desktop.  I turned off and disconnected the USB drive.  Nothing.  I thought there was a FAT32 HD size limit, but if there was, i should be able to add files after I delete some old ones.  Any IDEAS?I believe there is a 2G limit in FAT 32...you might have to convert now or use a file splitter.

Make SURE you have backups before converting to NTFS just in case...a Fat 32 drive can go up to 2 terrabytes with a 32kb cluster size

But not with a Seagate external data transfer disk. I really would like to know why ?
your only OPTION appears to be to format the drive to NTFS
there web SUPPORT site
http://www.seagate.com/ww/v/index.jsp?locale=en-US&name=SATA_Troubleshooter_-_4_GB_File_Size_Limit&vgnextoid=1b054a3cdde5c010VgnVCM100000dd04090aRCRD

says this

4 GB File Size Limit

Hard Drive Reports “Disk is Full” During File Save and With FAT32 Partition

The FAT32 file system has a 4 GB limit for the size of file that it can accept to be saved onto it. This means that any attempt to save a file that is larger than 4 GB will be met with an error message of “Disk is full or Not enough space” even though the hard drive may have a large amount of space still available.

Windows 98 and Me accept only FAT32 partitions, but Windows 2000 and XP accept both FAT32 and NTFS partitions. NTFS partitions have no limit for file size, so NTFS may be preferable for saving a file that is larger than 4 GB.
Ahh, said the blind man.  That explains it.  I was able to copy the smaller files, but not the larger ones.