Diskpart Mess in my Windows XP Pro

I was trying to make a USB bootable for the installation of windows 7. I followed the guide in this website:

https://www.intowindows.com/how-to-install-windows-7vista-from-usb-drive-detailed-100-working-guide/

I did steps 1 to 4. My 4GB flash drive was plugged and so was my 400GB external hdd (Phillips). It was too late when I realized that I did step 4 on my external hdd.
STEP 4:

SELECT DISK 1

CLEAN

CREATE PARTITION PRIMARY

SELECT PARTITION 1

ACTIVE

FORMAT FS=NTFS

(Format process may take few seconds) - this actually didnt take place (I dont know why)

ASSIGN

EXIT


Now, I cant open my external hdd - it always says your drive needs to be formatted.

What should I do? I am not that computer savvy (my OS is Windows XP SP2). I really hope someone can help me in this mess. Thank you very much.

HP 6510b
Intel Core 2 Duo T7250 2.0GHZ
1GB DDRAM
80GB HDD
Windows XP Service Pack 2

Rets