TYPES OF LAPTOP HARD DRIVES

Size and Speed

The current standard size for laptop drives is 2.5 inches.  There are some laptop computers which use 1.8 inch hard disks.
Laptop hard disks come in several different speeds including 4200rpm, 5400rpm, and 7200rpm.  Of course 7200rpm disks
operate quicker, however they consume more battery power. 

Interface

Parallel-ATA (PATA), ULTRA-ATA, or IDE
Introduced in 1986, this is the standard 16 bit parallel interface called ATA- commonly referred to as IDE (Integrated Drive Electronics).  It refers to a drive with a built-in controller which greatly simplifies installation into the computer.  It supports transfer of data up to 133MB per second.  Most desktop and laptop computers use the standard IDE interface. 

Serial-ATA (SATA)
Introduced in the year 2000, SATA was designed as an improvement over the ATA interface.  It is a 1 bit serial interface
that currently supports data transfer at a rate of 300 MB per second.  SATA also includes other benefits over ATA including
improved wiring, improved reliability, cyclic redundancy checking to protect data, and hot plug capability.

Capacity
The 2.5" laptop hard drives currently available provide a capacity up to 160GB depending on which model you choose.  The
1.8" laptop drives currently available provide a capacity up to 60GB.  In the near future, Seagate will offer new technology
that could include an increase in disk capacity by a factor of 10.  They plan to offer a 600GB 1.8" laptop drive and a 1.46TB
2.5" laptop drive.