Problem with iTunes download

[DEG_015]

so my external hard drive died this week (no big deal to me, lost my music but ive got it in other places)...but i also had itunes on my external HD, so i tried reinstalling itunes and whenever i try to it says Error:Invalid Drive G..G was the name of my external HD but if im trying to reinstall it now, why is it trying to save it to G and not Drive C which is my HD in my computer...anyone know how i could possibly re-route the installation so it saves on Drive C?