Question about computer mouse and keyboard problem?

So I fixed one of our cpu's that was broke about a year ago. I'm not very computer savvy, so I'm pretty stoked that I fixed it on my own. Anyway, we don't have the original mouse and keyboard(using one from our working cpu) so while they are plugged in and lighting up, it's not registering and working. i haven't done a system recovery, but when I went to that menu at the computer's start, they were working. However, when I left that and went to a normal start-up, neither registers again. Would a system recovery fix this problem? Any other tips?