Updating My Computer Security

I just bought a mini computer, and I love it. I haven't put any security on it yet though, and I know I should do that pronto. At work, we have Network Security Software that is someone else's responsibility. He knows the best kinds of software to put on, and what kinds aren't that great. At work we have both Antivirus and Antispam software, and that is wonderful. I remember in the early days of email, how bad the spam was. It is still bad, but we don't see it, because the software filters it out. That makes things much better! I just need to think about what I want to do with my mini. I had a program on my laptop, which I still use and I may use that program again.  And I don't want to spend a ton of money on it either. I have enough expenses right now, and I don't need to buy a bunch of expensive software. I am sure that if I spend some time researching, I will come up with a good idea of what would be the best solution.