Sharing problem in computer what i have to do?

Me and my flat mate both share a computer. The last one we had a turned of the power supply and it never worked again after that, I rightly got the blame for that one, then we bought this 2nd one which went on me, to the anger of my flat mate however we found out it was the fan that had gone so we took  the fan out of the other one and connected it up and works the problem is the fan is just next to the computer as it doesn't fit so the computer is completely open on one side with all the wires on show it's been like this for months and although it still works what could i face? with it like this. By the way I tried connecting hard drive to this computer it come up as hard drive  but i couldn't use any other programs.