Almost anything you can buy these days will be fine for browsing the web, word processing, netflix, etc. Get something refurbished if you can, and get something with a 30 day money back guarantee if you can in case it's bigger than you thought, doesn't run your program, or is otherwise not for you. I think amazon has a 30 day full money back guarantee on computers but you should double check that.
Most people should buy a laptop and a monitor, keyboard, and mouse to plug into it when you're home. If you really want to spend as little as possible and mostly work from one place, get a desktop; they tend to be cheaper than laptops.
If Macs can run the programs you need (they probably can), and you can spend the extra money that Macs cost, buy a Mac. The main reason for this suggestion is because they make backups easy, and they don't come with tons of crap installed by the manufacturer to subsidize the cost.
I have a 13” Macbook Pro laptop. I find that the right balance between portability and being able to see what the hell I'm doing when I'm out (I use it with a monitor, keyboard, and mouse at home). Apple has a little-known refurbished store.
If you play serious video games, especially recent ones, you need to be more careful that the computer will support it. Usually the thing you need to be careful about is the video card, aka video adapter, aka graphics chip. The game websites will often have system requirements listed somewhere and you may be able to compare what they list to potential laptop specs. Even better, search for someone running the game on that laptop, or as a fallback, on that video adapter, and see if they say how it runs.
If you play facebook games, you'll be fine with most computers.
If you're sure you want a Windows PC, you have to decide whether to get Windows 7 or 8. Some people like 8 and many people hate it because it changes some things we're used to and can be confusing. The best bet is to go to a local store like Best Buy or Staples where you can try a display computer running Windows 8 and decide for yourself. If you'd rather skip that, play it safe and get Windows 7.
Don't forget to buy backup software.
Last updated: 2014-02-05