lupetalo :
In order to use/try the program you have to make either bootable flash or bootable CD. I was dumb enough to make the former, but I didn't try it on my PC. Then I decided to remove the bootable files from the flash by formatting the flash
All you did was make a boot USB drive with that utility, it did not destroy anything. It just made a 2 GB partition when it created the boot disk. It's like someone taking a cake, cutting off 1/4 for you on a plate and putting the rest in the fridge. You still have the full cake but you just see 1/4 of it, you don't panic that someone destroyed your 3/4 of the cake, it's just not in front of your nose.
Run the HP utility already posted, it should wipe the disk again and put it back to full partition size. Or you can use the diskpart command line utility to delete everything off the drive with the clean command and then create and format the drive with disk manager in Windows.