Not a hack but more of an orchestrated attack. It was high school and our computer labs ran windows and all of them were connected to a central server. Now i had just learnt about windows api and how it can be used to check the space available on a disk. So i wrote a small script to to write chunks of 5mb files in the directory where TURBO C++ was installed and let it run till the system ran out of space.
Then in the spirit of conspiracy i added the said script to the central node and asked everyone in the lab to copy it locally and execute.
Then a few days later, the poor lab incharge corners me and say who added the ms91.dll file(do not remember the exact name😐). I said that it is a standard Microsoft dll and also how would I know. Then he goes on saying how he had to reinstall windows on all computers. At first I felt sorry but then the spirit of satan rose in me and I denied any responsibility about it and returned back to class where each of my classmates had a good laugh about it. 😂😂