In this node, there is already a lot of very useful basic information. I will summarize the bits I think are important, and add a few points of my own.

Kelrin points out that it is very important to check whether parts will work together. Especially with newer parts, there are often combinations that work buggy, or not at all. If a bit of Googling on the two part names reveals lots of cursing in hardware fora, you should realize that getting them to work is not going to be trivial or even possible.

Perhaps the best advice offered so far is that of LordOmar: Find a good store, and stick to it. Anyone who has been through the hell of incompetent 16-year olds in tech support, delivery times that get measured in weeks or even months and finding out the shop next door has the same part 30% cheaper will know why. I share his feelings about large-chain stores: they are often more expensive than small stores. I have had my best luck with very small stores, just a few friendly computer hobbyists opening a store. Because they are hobbyists, they tend to know their stuff.

I don't trust the salescritters in any shop, as their goal -making money out of me- is fundamentally opposed to my goal, getting the best value. Plus, their technical knowledge is not necessarily correct.

Many stores nowadays are web stores. They are often cheaper than brick-and-mortar stores, presumbably because they don't incur the overhead of a having a store building and people permanently manning it. People have sites rating webstores, be sure to check their rating before doing a major purchase. Better yet, do a small test purchase first.

If everything goes smooth, which is what normally happens, you will have your computer part delivered to your door, cheaper than in a normal store. However, if stuff goes wrong, the fact that you can't easily physically visit the store might work against you. If you buy a computer, spend those extra 50 bucks to have it assembled, even if you can do it yourself. When they assemble it, it gets tested, and the peace of mind to get a computer that actually works, instead of having to figure out which part is broken, sending it back, and potentially having to wait for weeks to get it send is well worth the money.

McSnarf makes a good point about price/performance ratio. However, I think that it makes more sense to apply this concept to your whole computer, rather than one part. Say you want to buy one of his Hoglons for your computer A computer is more than a processor, but this will be a simple machine, so all we need is a $100 hard drive, $100 worth of RAM, a $100 mobo with everything on it, a $100 case, a $ 50 optical drive and a $50 video card. That's about $500 total. This makes the list for the whole computer look like:

Processor Speed	Part	Total Bang/Buck
Hoglon 500 $83 $583 0.86 Hoglon 750 $97 $597 1.26 Hoglon 1000 $145 $645 1.55 Hoglon 1300 $160 $660 1.97 Hoglon 1600 $320 $920 1.73 Hoglon 2000 $982 $1482 1.34
As you see, the basic trend remains the same, somewhere in the middle you get most bang per buck. However, this graph shows how truly pathetic bargain parts are: For only a little bit more money, you could have a much more powerful computer, which would last you much longer before being obsoleted. In general, this shows the "sweet spot" is a little bit higher on the curve than you might guess from a simple bang/buck graph.

I will now discuss what is important to consider when buying some key computer parts.

Processors

The part most people equate with speed. There are at the moment two major processor manufacturers: Intel and AMD. I have no experience with the former, but products from the latter company have never let me down. People tend to equate processor speed with the megahertz rating. This is only partially true. Other things that influence the processor speed is its front side bus, its cache and, most importantly, its architecture. A given processor can run at twice the megahertz, have more cache, more FSB, and still be slower than a processor with a different architecture. This may also be application-dependent: a processor may be faster than another processor in one application and slower in another. Hardware review sites use benchmarks to compare processors.

Processors, provided they are cooled adequately, are one of the most reliable parts in a computer system. They are often supplied with a cooler which is sufficiently strong.

Processor coolers

If your processor is not shipped with a cooler, you will need to add one yourself. You might also want to upgrade the stock cooler. Processor cooling is very important: if your processor runs too hot, hard-to-reproduce crashes may occur. Processor coolers may make a nerve-wrecking racket. Slow, large fans are better than small, fast fans in this respect.

The case and power supply

The case houses your computer. It plays a key role in keeping your computer parts cool. It is often sold with a power supply in it. Make sure that this power supply is adequate. In particular the video card and processors can be huge power hogs, and getting a new one might make it necessary to upgrade your power supply.

If the power supply is not adequate , you might experience odd hangups. You can check whether your power supply is strong enough by reading your voltages in your BIOS. If they drop significantly, say, 5%, under their nominal value, your may have a problem.

RAM

RAM is the computers main memory. Make sure you have plenty. If your computer has too little, lots of swapping to the hard disk will occur, causing your speed to completely collapse. Especially if you want a computer that you intend to use for a while, make sure you have enough, as nothing can make a computer feel like an old nag like having too little RAM. It therefore is a very popular upgrade: just stick extra RAM in it, if it starts feeling slow.

What sort of RAM your computer can take depends on your computer's motherboard. This is also the reason you don't want to wait too long with upgrading your RAM: if your mobo can only have obsolete RAM, it will be hard to find RAM cheaply.

RAM also has a speed rating. Generally, the speed of RAM is not that critically important for the speed of your system, although exceptions occur.

Some motherboards let you use dual-channel RAM. In this case, you need an even number of RAM sticks, so, for instance, 2x512 MB instead of 1024 MB. If it is supported, dual-channel RAM should be faster than single-channel RAM.

RAM is often sold with life-long warranty. They either fail right away, or not at all. Broken RAM can give very hard-to-diagnose errors.

The motherboard

The motherboard is the big thing you stick all your stuff in. There are many different motherboard manufacturers. It is very important you buy a motherboard from a manufacturer with a good reputation. Motherboards are full of all sorts of electronic components like condensers and resistors, and many manufacturers use crap components to shave of a few dollars. Because there are so many components on it, motherboards are prone to failure, and you do not want to make this risk even bigger than it already is.

As I said, the motherboard is what you stick the rest of your stuff in. Hence, it determines what sort of stuff you can stick in. Want to stick in an certain type of processor? Make sure your mobo can handle it. Want to use dual-channel RAM? Check the specs. There are literally hunderds of types of mobos for sale at one time, but choosing is easy if you realize what you want to put in.

Many motherboards come with integrated features. This is quite great if you want these features, but not as great if you don't need them, as you will be paying extra for them. Some of these features are a substandard version of stuff you would normally buy separately, some are exactly as good.

The hard drive

This is what you store your stuff on. Hard drives have gotten remarkably large the last few years. For most people, a modest-sized hard drive will do. At the moment, the only thing I can think of that will eat heaps of hard disk space is video editing, or movies. If you want to do this, be sure to get a big one.

Hard drives are also rated with a speed in RPM. Due to mechanical constraints, this speed does not nearly increase as fast as the speed of other components. Typical hard disk data transfer rates are more than 100 times slower than the RAM data transfer rates. If your computer has plenty of RAM, however, these transfers are relatively rare.

It is possible to use 2 (or more) hard disks in a computer in a so-called RAID array. This may be used to increase the reliability of the system: If one disk breaks, not all data is lost. If you weigh the cost of hard disks and the value of your data, it soon becomes clear why this is often a good idea.

The video card

In the old days, a video card did little more than putting stuff that the processor spat out on your screen. However, nowadays, there are video cards with processors and RAM on them that compute largely for themselves what the image on your screen will look like. Because they are dedicated to this purpose, they tend to be much better at this than the processor. This is especially important for playing games, in particular First-Person Shooters.

This particular branch of computing is evolving at a pace that is even more frantic than the rest, and any information you have today is hopelessly outdated 6 months later. I suggest using benchmarks when making the decision which cards to buy. The absolutely incomprehensible marketing speak does not make it any easier as well, and an extra letter at a strategic place in the name can be the difference between a speed demon and a sorry nag.

One thing that is worth pointing out is that while the amount of RAM on such a card is often loudly advertised, it is usually not the most important thing for the card's performance. The habit use of slower but more RAM on some of these cards may in fact harm rather than help performance.

In summary, knowing what computer parts to buy is not simple, even when barely scratching the surface, like in this node. Worse, specific information about the subjects tends to become obsolete in months, not years or decades. There are two good ways of brushing up on the specific information:

  1. Read on the Internet: there are tons of dedicated hardware sites
  2. Ask a (hardware) geek you know
Because the stuff written on the Internet is generally written by geeks, the two options generally are roughtly equivalent. Yes, there are websites and fora with hundreds of members dedicated to the matter of burning CD-ROMS alone. They know more than you do. Learn from them.

Hardware geeks do tend to have a bias towards the best -and therefore most expensive-stuff, though. So, if you consult one, be sure to make sure he will address your computing needs, not his uber leet needs!