I want to re-install itunes to my windows 10-64 laptop, I run the program to install, but at the end it tells me there is an error and to run installer again, ut there is no option to allow me to do so

I have a Toshiba satellite E55t-A5 running windows edge 10-64 bit. I keep crashing and losing my programs. I want to install iTunes again. I run the install program for latest windows program and it lets me get to end and gives me an error message, stating that the program is not modified and I need to run installer again, but gives me no option to do so. How can I get program re-installed again?