Hello Giuseppe.
Allow me to repeat the problem to make sure I understand correctly.
Step 1
You successfully installed LL to your PC's hard disk (sd1) using a Live usb key as the source for the installation?
Step 2
You would like to boot the PC (in step 1) using the Live usb key (in step 1) and install LL a second time to a new usb drive?
Allow me to repeat the problem to make sure I understand correctly.
Step 1
You successfully installed LL to your PC's hard disk (sd1) using a Live usb key as the source for the installation?
Step 2
You would like to boot the PC (in step 1) using the Live usb key (in step 1) and install LL a second time to a new usb drive?