Section 1 - From The Ground Up
When the thought of building a computer comes to mind most people think to themselves that it's a very hard and arduous task. This is in fact not the case most times. In actuality it's very simple and is usually a pretty quick process. When building a computer the parts you buy pretty much only fit in one way and almost all parts (OEM not included) come with manual's, driver disks, and little accessories to make your life easier.
Section 2 - Choose Your Path
The first step in really building your computer is which path do you want to take, Intel or AMD. The general consensus is that AMD is made for gaming, while Intel is made for multitasking and processor intensive work. To see what the real differences in the chips are the best thing to do would be to read the CPU 101 created by Praetor. It outlines the types of chips on the market and gives info on what to expect and what not to expect from each chip after you purchase it and stick it in a system. Now as this thread is only a guide on how to put your machine together you'll have to decide what parts to buy on your own, or search on the forum or computer review sites for the parts that best suit your needs.
Section 3 - Purchasing Parts
When buying your parts you're gonna want to look for the cheapest price usually with the least bit of hassle. If money is of no option to you then it won't really matter if you buy your parts online, down the street at your local computer store, or at a major company such as CompUSA, BestBuy, Circuit City, or the like. But if you're like most people you're gonna want to find a deal. As for this there are more than enough companies and places online that sell computer parts and accessories. To find the right sites is indeed the key. A site that is commonly used just to get a bearing on what you should be paying is
http://www.pricewatch.com It shows the lowest prices per part and then the lowest prices per distributer. So if you were looking for the newest Intel chip out there pricewatch would show you the lowest price on that specific chip for each site or company offering it.
Section 3a. - Specifics on parts:
This section will provide just a brief over view on what you might want to look for in your parts. It won't tell you exactly what parts you should buy, but merely a guide to point you in the right direction when you're buying parts. For information on some parts and what you might want to buy I suggest reading the 101 threads written by Praetor, some important ones are as follows.
CPU 101
HDD 101
PSU 101
RAM 101
CD/DVD 101
CPU: Mind you, when you buy your CPU you're going to have to buy a motherboard and ram that go along with it. All the major motherboard companies makes their own variations of their boards for Intel and for AMD. To find the right one you'll have to first decide what you'll be doing. Generally speaking AMD is for gaming while Intel is for processor intensive tasks or a lot of multitasking. If it's going to be an all around work machine then it really doesn't matter which path you take.
Motherboard: With buying a motherboard there's more than one thing that needs to be considered. Which chipset do you want, which CPU are you using, what onboard functions do you want. To find the one that suits you best you need to take into consideration what you'll be doing with your machine. If you're going to be a hardcore gamer you're going to want stability and possibly a nice board that won't fail while being overclocked and a board that has PCI express or AGP or whatever you plan to use. If you're going to be running a high speed machine with it being largely overclocked you're going to want a board without all the bling and with more of the stability factor than the ability to run stuff you'll never need. If it's going to be a general work computer (email, word, viewing pictures etc.) you're not going to need the top of the line board or one with the stability of an ox, just one that can do what you want it to do because you won't be putting it through major stress.
Memory: Memory is an integral part of the system and depending on what you're doing you again don't need the top of the line memory, memory standard is something that's important though. Generally speaking the standard of memory is that of 256Mb CL3 of a brand name (Micron, Samsung, Kingston, OCZ, Corsair, Crucial, Geil) in 1 or 2 sticks depending on if you want/have dual channel mode. For most systems 256Mb will be fine if you don't do anything intensive such as playing the latest games or rendering full scale movies in real time. If you're a gamer you'll generally want 512Mb CL3/2.5 memory of a respectable company (listed above). For the hardcore gamer 1Gb (1 or 2 sticks) might be the necessity for you (CL2.5/2) depending on what games your playing and at what settings and whether or not your board/chip supports dual channel mode. Another factor to take into consideration is what speed and type ram can your motherboard handle, PC2100, PC2700, PC4200, SDRAM, DDR1/2, etc. If you buy the wrong speed or type of ram you risk loosing performance and in some cases stability. Each speed and type are different (obviously) meaning that PC4300 DDR-2 RAM will most likely out perform PC2100 DDR RAM and may not fit in the same motherboards. It's up to you and to the specifications on the motherboard which ram you ultimately end up buying.
Graphics: The Graphics card is another integral part of the system you're building. Buying the right one can be a deciding factor on what you can do with your rig. If you want to make the high end gaming machine you've been dreaming about you're not going to go out and buy a graphics card from 10 years ago. If you're going to make an old machine just for word, email, and the like then you can save money by not buying the brand spanking new 500$ card on the market and simply sticking with an old 32 or even 16Mb graphics card. The graphics card you buy can be determined by what ports you have on the motherboard you are purchasing. If the motherboard only supports AGP1/2/4/8x then you will be looking for an AGP card that fits with the board. If it's a board that supports PCI Express or SLI then you need to find yourself a newer card such as the Nvidia6600/6800 series (Also made in AGP) or the ATIx3/6/800 series (Also made in AGP). The card depends also on how much do you want to spend, and what kind of performance do you want/plan to get out of it. The final decision to buy the card however is up to you.
Hard Drive: Hard Drive (for those that don't know) is what stores everything you have on your machine. So whatever size Hard Drive you have is how much data or "stuff" you can keep on your machine. Base HDD's now a days are 7200RPM in either PATA or SATA format (not including SCSI drives). The average size is anywhere from 60-500Gb per drive. Since prices are at an all time low now it almost doesn't matter if you buy PATA or SATA for your computer. However if you're doing things such as major gaming you're not going to want to buy a brand new 6 disk SATA array and setup a RAID 5, a single SATA or PATA drive would be enough for your needs. If however you were going to be running a storage comp as a server for games or as some sort of hosting device you might want to spend the money and setup a nice SCSI or SATA array. In most cases however a single drive (like mentioned) will be ok for almost anyone's needs.
Cases: The case is just that, a case that houses your components. There are many different types of cases in many different shapes, sizes, and colors. To find the one that's right for you it sometimes comes down to personal preference or the amount of money you have available to spend on the machine. There are base models, and then there are high end models. Some with 2 fans, some with 8 fans. Which case you buy is up to you and what you want it to A. Look like or B. Perform like.
Power Supply: The Power supply unit (PSU) is just that, it's what gets the power to your machine. It's what gives all the parts their juice. So if you buy a crappy power supply then you get just that, something that you can't trust to run your system correctly. If you buy a beast of a power supply that's ok, you'll get a nice PSU that runs your system with good overhead. If you're a gamer or if you're a base user the PSU should always have at least 18-20Amps on the 12 volt line. Any lower and you'll be playing with fire to see if it will support your system. If you're a hardcore gamer you're gonna want to buy a decent PSU with a nice stable 12v rail that has a good amount of umph behind it (somewhere in the range of 26-32A).
CD/DVD Drives: DVD, CD-RW, DVD-RW, there's so many choices it's sometimes hard to decide. Depending on the machine you can buy many different types of drives. If you want to just have a drive to backup your data on you might want to consider buying a CD-RW (CD-ReWritable) drive or a DVD-RW drive. If you don't ever plan to burn any data from your computer onto a CD or a DVD then you can stick with just a normal CD-ROM drive. However with the prices of drives now it's more worth it to spend the extra 5$ to buy a CD-RW drive than it is to buy a regular CD-ROM or spend the extra 20$ to buy a DVD±RW drive or Dual Layer drive than it is to buy a normal DVD-ROM. Whichever drive you buy they will all be able to play the same media but not necessarily read or write the same media.