Help with Executable files!!!?

a couple of days ago, i download a .exe file and when i clicked run, nothing happened. on the second day,norton 360 encountered a trojan horse virus.so i removed it. on day 3, i turned my pc on and and out of nowhere the .exe file asks me if i want to run or cancel, so i click "cancel" and the same thing happens 2 more times!!!!!! please help me!!!!! what should i do???