Game constantly crashing

Got a new computer a few months ago. Didn't realize until I bought it that it doesn't have the capacity for the game. I bought a plug in hard drive to fix the problem, and it worked for the first few months. I went on a trip and had my computer without my hard drive for a while. When I plugged it in again, my game started randomly crashing and closing about every half hour. I've gotten used to saving every few minutes, but it's become more frequent and it's getting really difficult, I've tried repairing my game multiple times but nothing seems to work. Any suggestions?