I suggest getting a local shop to put together a computer. I'd recommend Ubuntu Linux as the operating system (it is free). The local shop will put it together. Gives you Firefox web browser and a mail client for your emails. Pretty much bullet proof. Also, it will tell you when new updates are available and ask you if you want to update. Finally, there are not a lot of computer viruses that target this system, so you don't have to be concerned about that.
Depending on your needs, I'd recommend saving money by asking for an I-5 processor. Get 4 GB ram. Get high speed ram. Discuss this with the shop. Depending on what you use the computer for, you might want to get (2) hard drives and ask the shop to set it up to run automatic back ups.