99nasha's guide was great, but as stated, it was very brief. Here, I try to offer you a compliment to his guide.
**SKIP TO MIDDLE IF YOU JUST WANT THE HOW-TO
First off, I'd like to make it clear cut that overclocking not only applies to processors, but also to video cards and RAM. This guide will deal mostly with CPU and RAM overclocking. The concept can be applied to video cards.
I don't think 99nasha stated it, but not all computers can be overclocked. Computers bought from a manufacturer (ie: Dell) have a locked BIOS standard. A locked BIOS means that the user is not able to change any settings regarding the CPU, RAM, and some features of the motherboard.
As 99nasha also stated, your computer CAN be damaged by this process, however it is very uncommon. The most severe damage comes from raising the VCore. The VCore is the voltage used to power the CPU. When this value is too high, and you don't have proper cooling, your CPU can light on fire. Raising the frequency and the multiplier to an overall higher clock does not actually hurt your processor, because without the proper voltage, your computer simply won't boot up. The other damage caused by overclocking is deterioration. Over time, a safe overclock will shorten the life of a processor. Fortunately, by the time your CPU is dying, you're already buying a new computer.
There are a few "requirements" if you want to have a truly successful and mean overclock. The most obvious is cooling. You need an after-market heatsink. The best around is the Thermalright Ultra-120 Extreme, known as TRUE(120). Secondly, you need a good motherboard. This is one of the biggest culprits of a sloppy overclock. If your southbridge (for AMD) isn't good (lower than SB750), then your overclock probably isn't going to be very good. [Intel's new architecture is a bit different, you shouldn't need to worry about this as much] Another equally important component is the MOSFET. Frankly, I'm not exactly sure of it's purpose, but when you overclock this component tends to get really hot. If you're having trouble with your overclock, look to buy a heatsink for the MOSFET; it could just solve your problem.
Here's a picture for those of you who don't know what the MOSFET looks like:
Lastly, you need to make sure you get some good RAM (most Corsair, OCZ, and G.Skill overclock very well). RAM heatsinks aren't a necessity. If you want to overclock you RAM, you need to make sure the sticks you get a friendly with voltage changes.
I won't beat around the bush anymore, so let's get right to it!
START HERE IF YOU JUST WANT TO KNOW THE HOW-TO
The first step in getting a good overclock, is determining the maximum frequency that your CPU can handle. To do this you must lower your multiplier and your RAM frequency values. Since a CPU vary with their stock clock speed, you'll have to determine how much to lower the multiplier by yourself. The RAM should be lowered to the value immediately before it's stock value. If you're wondering, the point of all this is to prevent any bottlenecks while figuring out your max frequency value. You can now start testing.
The test is very simple, it consists of the following:
1. Go into your BIOS and raise your CPU frequency by 5.
2. Boot up and run P95 or Orthos for 10 minutes.
3. If you've successfully survived the stress test, go back and raise the frequency by 5 again. If you failed, decrease your frequency by 5, and raise it by one.
4. Repeat stepts 1-3 until you've found out the absolute maximum value; this is your raw max CPU frequency.
When you've found this value, go back and set your RAM and CPU frequency back to stock. Then, repeat the test, but this time, run Memtest86 or some other stress test on your RAM after the CPU stress test. If after all this you have the same max CPU frequency number, then you don't have a bottleneck. If you don't, then your RAM could possibly bottleneck your overall overclock; you'll have to determine this later. For the rest of the guide, I'll refer to the max CPU frequency with RAM as max freq.
Now that you've found how much frequency your motherboard can handle, we can start to get some raw power. In another words, we're going to start raising your clock speed. Since this is a lot of trial and error, I'll give you an example of how you can go about doing this.
REMEMBER: FREQ x MULTI = CLOCK SPEED
Set your multiplier back to stock. We're going to with only raising the frequency and the VCore.
1. Boot into the BIOS.
2. Raise your frequency by 2-5 (depending on how high your multi is)
3. Boot up into your OS and run the stress test for 10 min.
4. If you pass, repeat steps 1-3.
5. When you fail, you also repeat steps 1-3, but raise the frequency by 1 until you find your absolute max.
6. Now, go into your BIOS and raise your VCore by .025.
7. Repeat steps 1-6 until your core
temperatures are 10C off its manufacturer's safe maximum.
It is important that you keep an eye on your temperatures while you do the CPU stress test. Don't let them pass that mark that is 10C below the manufacturer's maximum safe temperature.
Once you find your top CPU
overclock through this process, you can go back and refine it. The way you do this is simple, you want to have the highest overclock with the highest frequency. This way, you get the most out of your RAM and your CPU. You'll most likely have to lower your multiplier to do this. [AMD users should be careful that odd multipliers result is lower RAM speed compared to even multipliers. You'll realize the difference by experience].
1. While testing your overclock, ALWAYS
keep an eye on your temperatures.
2. Always keep the CPU-Z screen open during testing. Write down the VCore value before you start the CPU stress test, then write down the lowest value in this box during the stress test. This drop in voltage is called VDroop and is one of the reasons you can't raise your overclock at the same rate during the entire process.
3. If your computer doesn't boot, you've raised your VCore to a value your motherboard doesn't like. You'll have to reset the CMOS, so make sure you're always writing down your best overclocks.
4. You'll get a few for how your RAM and CPU respond to raising certain values. You'll discover the tendency. Once you've found this and you realize the pattern, you're able to take some short cuts. You'll see what I mean when you start messing with this.
5. Realize that overclock relies a lot of trial and error. Your computer may like high frequency and lower multi or vice-versa. If you keep trying different combinations, you'll find the golden one.
If you have any questions please post! Overclock is an extensive process and I'm sure I missed a few points on this guide. I'll have to iron that out over time, as I re-read it throughout the following days. There are quite a few members here who have more experience than me in this field. I write this guide with them in mind. They were the ones who taught me what I know. Feel free to PM them with questions because they'll know how to answer it better than me.
Here are some of the masterminds:
-A True Folder
There are more, but I can't think of your name right now, (sorry it's late).
Thanks for reading! Good luck!