Reinstall Operating System Over and Over

I dont know what happen with my computer, it so many error, my friend tell me that my computer had attacked by virus and it must be reinstal my operating system. Before it, I have so many times reinstal it, and i wonder that could it bad to my hard drive. So, i search in internet to find the answer. And the result, it is completely false. Harddrives are made to be read from and written to and all this does is writes and reads files. Reinstal Operating System not bad for hard drive, the only thing worst is its just waste time.