Removing Ubuntu from new Install

New to Ubuntu and yesterday I installed in my Windows 8.1 laptop Ubuntu Desktop. Eventually I was able to log to my new install but when I logged out I was not able to get in again (in my boot menu I had 5 new entries related to Ubuntu) and no matter which one I selected I was getting a black screen with codes instead the Desktop I got the first time.

Anyway today I decided to remove Ubuntu from my laptop and install it in an old ASUS desktop I have which has no OS. The installation is in progress right now and so far all is good.

Trying to remove Ubuntu from my laptop I used the same ISO I made yesterday but there in nothing about removing it on the ISO menu. How can I remove Ubuntu from my laptop?

Thank you