Step 1: Knowing what you will use it for
How powerful do you want your computer? What are you going to use it for?
Before you go out and look up all the parts avaliable, realise what will be used on the computer. High intensity games, web browsing or just some microsoft word. Depending on what you need it for will also determine the price.
For web browsing and micrsoft office you could put together a brand new computer for $500. Dont let the price fool you, my parents went out and bought a hp computer which ended up costing around $1400. Even with purchasing better produces which would have exceeded that computer in all areas, aswell as allowing my younger brother to play fairly recent games, i could have put together a computer for around $800.
Who will be using the computer? What will be used on it? Web browsing and office does not require much computer power and can get away with a cheap system which suits your needs for only a couple of hundred dollars. However if you are wanting to build a pc for new games and you are wanting to play them on high settings with a decent performance and good frame rate, them u will be spending between $1000 to $2000 depending on how enthusiastic you are.
Personaly i have just built a gaming computer that cost me around $1800, including a 22″ screen. This is able to play any games on maxed out settings and still perform at a good rate. Crysis with full settings (no AA), maintains an average of 25fps.
You have to decide what you will use it for and put a budget on it respective to what you want it to do.
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