Hard disk drive stores all your data including operating system, applications, user files and documents. It is a non-volatile storage, which means the contents of the HDD is not lost if the PC is switched off.
There are three different types of HDD, which are IDE/ATA, SCSI, SATA (Serial ATA). Majority of home PCs are equipped with IDE Hard drives. SCSI hard drives are mostly included in servers and powerful workstations as they offer better data transfer rate which results in better performance than the IDE drives. However modern SATA drives are not far behind SCSI drives in terms of performance with the introduction of the newer SATA 300 drives.
The price of IDE/SATA drives have fallen quite dramatically in the recent years. You can buy a very large drive for a competitive price. It is better to buy a drive which is quite large as it works out cheaper. A recommended entry level drive would be 80 GB to 120 GB. The major HDD manufacturers are IBM, Seagate, Maxtor, Samsung, Western Digital and Fujitsu. For our demonstration PC I have chosen a Maxtor ATA100 drive as shown below.