I created a usb directory in /mnt , then I ran the command
I get a error message saying "mount: /dev/sda1 is not a valid block device"

My usb is LexarMedia (512MB).

I am running Fedora Core. The /dev/sda1 does not exist. I ran the command
Is there something I am doing wrong? Can someone help me with this. Your help is appreciated.

thanks in advance

run dmesg to find the location of the drive.

unplug your usb device.
Wait a few seconds then plug it back in.
Then type: tail /var/log/messages

This gives me the address of the usb device.

Then do your mount command plugging in the right sd** info.

I had a similar problem with a usb key that wouldn't give me a /dev/sda1 entry, only a /dev/sda one. After one yer of pesting against my Mandrake (it worked with aurox live) I tried mount /dev/sda /mnt/usb instead of complaining about the absence of /dev/sda1. And it worked, cause the data was directly written to the key, without any partitionning.

Also, it may be that linux got a wrong /dev/sda1 position. try this :
dd if=/dev/sda of=/home/you/usbdata.img
and as root :
i=0; while ! mount -o loop,offset="$i" /home/you/usbdata.img /mnt/usb; do echo "$i" i=$[$i+1]; done
This will try getting the begining of your partition.
When you get bored, press control+c.