windows vista freezes to update itunes

iTunes 12.1.2

I have install itunes already but yesteday I had a frustating day with my iphone I called apple for help theyre like I needed to update iTunes in my laptop so I did now my laptop is worse I get an error 7 and some other words. I cant uninstall nor download becuase my computer screen just there and it freezes it doesnt do nothing I gotta take of the battery. By the way the laptop is a windows vista. Why is doing me this ? its frustating