Drive c is unstable help me please?

okay so i had a virus on my PC from my school, because our flash drives transferred them, so i reinstalled my PC and when i was doing it I was missing a file while it was downloading put i continued to press skip. I know have the problem of installing my Sims game again. Problem is that when i install the game and the game tried to put something on my PC they asked me which drive to save it on..I originally put it on Drive C but that drive is unstable and cant be added to b/c it is unstable. Then when i tried to save it on the new local disk it says that it doesn't have space but if it is the local disk why does it only have 3.5 MB or something like that. Then I tried to re reinstall it and when i tried to partition the drive c they told me i couldn't do that since vital info for the re installment was in this drive..help me why is my stuff acting so dumb.. If no one can help me i guess i have to resort to best buy