Compatibility Form factor: Fitting the drive in the case, and thus are applicable only with internal hard drives. Desktop and tower computers are standardized for the 3.5-inch form factor, although it is possible to use smaller drives in one of these computers. UDMA: The speed of data transfer between system memory and the hard drive buffer measured in megabytes per second and, at the time of this writing, has possible values of 33, 66, 100, and 133. Check the motherboard’s max transfer speed and select the fastest hard drive the user can afford. Motherboards can accept any drives rated at their max speed or slower. EIDE or SATA: Some new motherboards have connector for both, but older boards accept EIDE only. SATA expansion cards for PCI slots are available. Quality Warranty: Before came with 3yr warranty now mainly 1yr. Try and get 3yr. Buffer: High-speed memory that is used to store a small amount of data while it is waiting to be read form or written to the drive. The bigger the better. 2MB good, 8MB much better. Less than 2MB likely to provide poor performance. Platter speed: The most common speeds are 5400 and 7200 revolutions per minute (RPM). The faster the platter spins, the faster data can be accessed and transferred. EIDE or SATA: SATA drives perform faster and more accurately than EIDE. Added advantage is that SATA cable are smaller, making for easier installation and better airflow.
FAT: Original DOS and Windows file system. Storage efficiency is the lowest and it is highly susceptible to fragmentation. Limits file names to eight characters plus a three-character extension. Max partition size for FAT16 is 4GB. Only file system accessible in all versions of Windows and DOS and only file system usable by the original version of Windows 95 and older. It is the file system for floppy disks. FAT32: Stores files more efficiently than FAT16 and has support for long filenames. FAT32 drives can be read by every version of Windows since the second version of Windows 95 (except for NT 4.0), and is the default file system for 98 and Me. The max partition size for FAT32 is very large, although there is a 32GB limit in Windows XP. NTFS: Original version of NTFS was introduced with Windows NT. A newer version was introduced in Windows 2000, and it is the default file system for 2000 and XP. NTFS is somewhat resistant to fragmentation and allows for many of Windows 2000 and XP’s security features not available in FAT16 or 32. The max size for an NTFS partition is two terabytes (TB), which is 2048GB. Windows 9x and DOS cannot use NTFS.