I am following the tread how to install Slax BackTrack 2 on my laptop - usb stick.

I have run the following commands:

fdisk /dev/sdf1
And then I press "n" as advised in the tutorial.

Then I get the following error:
You must delete some partition and add an extended partition first
Thus I google the Internet and this forum, and I saw somewhere that I have to look if the USB device is mounted. Thus, I pres /mnt. And yes, its showing up here, is that not good? And how to fix this error?

Thanks in advance!