There are a number of reasons why one needs to reformat your computer. You may want to do it on a regular basis to ensure that your computer is free from viruses and other types of malwares. You may be forced to resort to reformatting when your computer is unable to function correctly due to conflicting software issues or other problems. Whatever the case, reformatting is actually quite a simple process that most people will be able to perform on their own.
First, you need to copy all the data that you need that is currently in the computer that you want reformatted and backup it in an external hard drive or some other external storage device. Reformatting your computer will erase all data from your computer, so it's important to remember to perform this step and backup your essential data. It's still possible to retrieve data after you have reformatted your computer, however, it'll be a much more troublesome process compared to if you had backed up your data in the first place.
Next, insert the installation CD for the operating system that you are using. Depending on your operating system, the instructions and steps may vary slightly, but you should be presented with the option to reformat your computer (along with a few other options). Choose that option and your computer will start reformatting. The process may take quite a while, so find something to preoccupy yourself with while you wait.
After you have reformatted your computer and restarted it, reinstall all the programs and drivers that you need. If you have somehow omitted to backup one of these, and you can't find a replacement, it's possible to reconstruct the data using a data retrieval program. You can find one of these available for free on the web, although it may take some searching before you find one that you can use. The process of searching for that particular program that you want, among all the other data that got reformatted, will likely also take you some quite some time, so try to ensure that you have already backupped everything to save yourself from having to go through this step.
After reformatting your computer, your computer should be running faster now, and that any problems that caused it to function incorrectly should now be gone. If the problems still persist, it is likely that the cause is not a software problem, but rather, caused by your hardware.