One of the most problematic ways of optimizing your Windows PC is to format it. It involves some preparation, but we'll be giving you some easy tricks to get through this so that you can speed up your computer and free up some hard disk space.
We've mentioned before some of the steps involved but we left out some details. The most important thing that you need to remember is that if you are formatting your hard drive, you will erase all of the files and data that you have saved on it. So you will need to archive this by moving it to an external USB drive or another hard drive that's inside you PC. Most computers have more than one hard drive. The main hard drive is usually C:\ and the other drives are D:\ or other letters. It's one way of getting rid of some very nasty computer viruses that regular maintenance can't eradicate.
However, you need to be careful since some large hard drives are split up into C:\ and D:\ just to make them more manageable. If you aren't sure, it's best to double check before starting the format. You can format a PC without erasing these partitions. You'll just have to select the right drive C:\ to install the new OS.
To start off with, you'll need your original Windows DVD. All of this DVDs are bootable, so once you pop them into your computer, all you have to do is restart your computer and then follow the prompts. If you don't have the DVD, but have a downloaded version of this, it's usually easier. All you need is to click setup and remember your registration number. If the DVD isn't booting for some reason, you'll need to enter the BIOS menu. To do so you'll have to press either F6 to F9 just as the computer boots. It will depend on what kind of a BIOS your are running. Once you are in the BIOS, you'll need to use the arrow keys on your keyboard. The mouse won't work.
1. Press F6-F9 to enter BIOS
2. Select 'Boot' or 'Boot order'
3. Change the order of booting by putting your DVD drive first. You'll have to select a new order, usually a) DVD drive b) hard drive.
4. Press the key to save and exit
5. Restart your computer
This will force your computer to boot from the Windows DVD. All that's left is to follow the prompts and install Windows onto the C:\. This can take between 15 and 45 minutes, depending on how fast your computer is. If all goes to plan, don't forget to change the boot order once your finished.
(Images: Flickr member Jorge Franganillo licensed for use under Creative Commons, Flickr member Pam Pham licensed for use under Creative Commons)

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Your computer's BIOS may use an F key other than F6 or F9. Mine uses F2. Best thing to do is just restart the computer once and pay attention to the boot screen before Windows loads. It'll be listed somewhere on it.
Often, your BIOS will also offer a boot menu/startup menu--also mentioned on that same startup screen that lists the F key for your BIOS setup. It's much easier to just hit the designated key on startup and choose your optical drive from the boot menu than to change the boot order on your BIOS.
Formatting and reintalling from a back up or from "scratch" [I don't wish that it on any novice] is too drastic cure if the need is only to tune up a PC! Please buy Utilities software. Back data files, Clean up your too many icons on the desktop, purge temp files, duplicates, caches on your own as much as possible and or cautiously using the recommendation of the Utility package. Run a hard drive scan and any repair, then defrag. Let the program also backup then compact and defrag the registry after that. Then back up you data and the system to replace the earlier backup. If you keep the PC 'tuned' you may wear out a machine after years of use rather than have it slowdown unless it is a "lemon."
@verily
The last windows laptop I had was F2 also. As well as I think every other computer I can remember.
use a cloning program like clonezilla to make a perfect copy of your machine. http://clonezilla.org/
formatting and reinstalling all the updates, patches, software, and files takes a while.