1.Static electricity can seriously damage the components inside a computer. To avoid this you must ensure you are grounded when operating inside your computer. One way to do this is to purchase an anti-static wrist strap which you should wear at all times. The wrist-strap plugs into an electrical socket which will automatically discharge the static electricity in your body.

2.If you don't have one then every one minute touch the back of the tower where the metal is. The static from your body will go there.

3.The hard drive.A hard drive - which is also called a "hard disk" - is much like a filing cabinet. The programs and data are stored on the hard disk and the computer accesses them as they are needed. When the computer accesses the hard drive, it is reading and moving the stored information into the RAM memory. That memory is the temporary workspace. However, the original file is still on the hard disk and is left undisturbed until the file is saved.

4.When the computer stores or "saves" information, it writes the data to the hard disk. That process results in the old file being replaced or modified with the new information. If you save data to a new file, or install new software, the information is written to the disk in an available, unused portion of the disk.

5.Getting into the tower. Open both sides of computer case by removing screws at the back of the tower and sliding the panels off.

6.Removing the cables. Remove the data cables and power cables from the back of the old drive.
 
7.Unscrewing the drive. The drive should be held in place by screws on both sides of the tower. Remove the screws with one hand supporting the drive. Once the screws are removed slide the drive out of its holder.

8.Matching the jumpers. Once the old drive is removed, look at the position of the jumper on the drives rear. This jumper tells the drive whether it is the computer's main drive or auxiliary drive, so you must make sure that the new drive's jumper is in the same position as the old one.

9.Install the hard drive. screw the drive in and replace the data and power cables. Then replace the tower's side panels.

10.Re-install your software. When you have switched the computer on you will have to re-install all your software. Start with the operating system then all the others you require in any order. On a PC the operating system is generally Windows, on a newer Mac it is generally Mac OS X.