I have an usb external hd that i used to get working on other distros ( like fedora 1 ) :

with slackware 9.1 and current i could mount it as /dev/sda1 and read the files in it, but when i try to copy them on hd it fails the transfer!

What could i do?

thx in advance and sorry for the bad english!

Mount the filesystem, and verify that you can read files on it. If not, try using root until you get the filesystem permissions ironed out.

I'm not sure what you're doing now - but try using the cp command to copy files off the drive, instead of trying to move them. So if it's mounted as /mnt/sda1, you could do:
cp -r * /mnt/sda1 /tmp

Any additional info you can post would be helpful, like what command you use to mount the filesystem, and the command you use to get files off of it. The contents of /etc/fstab would be good too.

to mount the hd:

modprobe usb-storage
mount /dev/sda1 /mnt/usb

then i can read the files and i can also copy small files ( like jpeg images ), but when i attempt to copy a file bigger than 1 megabyte it fails.......