My external USB HDD wont show in fidsk -l or in my computer, how do i go about mounting it?

Older distros were not that good at auto-mounting USB HDDs. You do not say which distro you are using.
Plug in your USB disk. You might have to press a button on it to get it to "wake up". Then try the following commands (you'll probably have to be root):
tail -20 /var/log/messages
dmesg
If you are lucky, you'll see something to the effect that the kernel has detected your disk and assigned it to something like /dev/sda1. Now you know where it is, you can go ahead and mount it.
If you do not see useful kernel messages, do you have the appropriate usb modules loaded (lsmod | grep usb)?


HTH

check my output
http://pastebin.com/829050

You are running ubuntu kernel 2.6.15 on an AMD64.
Strange: lsmod shows you have the correct usb modules loaded.
But there is no indication at all that your USB HDD has been recognised. You did plug it in and turn it on I suppose?
[] Does your HDD spin up when it is plugged in?
Other things to try:
[] Use another USB port.
[] Try a different USB cable.
[] Try a different USB device.
[] Do any USB devices work?
[] Is there anything in your BIOS about USB that needs to be changed perhaps?

HTH

it was just a cable fault! thanks! so simple