You can save some money buy buying refurbished, or open box desktops are fine, laptops I never had one that last more then 1.5 years. If you buy a used laptop buy a protection plan that is at least 2 years. That way if it dies on you you either can get it repaired or replaced.
I do have a side note: If your computer is mission critical, have a back up a computer. I can't tell you how many times customers try to make it the repair faculty responsibility because the computer is broken. If you are a business owner or student that can't live without your computer make sure you have your data backup daily or weekly, your programs with activation codes (windows, office ect) is in a safe place, and have a backup computer. It can take up to one or two weeks to get your computer up and running again. This will save you much stress & anxiety, and just remember your computer will break down someday we just don't know when!
Free Self-Help link: http://www.columbusfinancialcoach.com/Cheap-City-Free-Guide.html