what are the difference between primary, extended,primary,logical etc partitions? what are their uses?

Hmmm. Yeah, This might take a little while to explain. I'll try to keep it simple Your primary partition starts at sector zero on your hard disk (the beginning sector) This is the one you use to boot your computer. In DOS-Based systems, this is always your c:\ drive. From there we go to the extended partition. It starts where your primary partition ends. In most cases it goes to the end of the disk as well. It is assigned no drive letters. In order to use it you must create logical drives in it. Logical drives are just the way drive letters (d: e: f: etc) are assigned to sections of the hard disk within that extended partition. If that didn't explain it, feel free to email me for more info.

A hard disk contains at HD addr 0,0,1 (head, track, sector) the master boot record (MBR, 512 bytes). This MBR contains the parition table, with up to 4 entries, specifying their start, end HD addr, size, type, flags, ... At boot-up, the MBR looks what is the active (bootable) partition (given in the flags), read its first sector (the boot sector) by its HD address at the absolute address 0:7C00h, and jumps there, and the small code contained there loads (boots) the OS. Up to v3.xx, MS-DOS had a 16-bit sector number addressing, what gaves 64K*512bytes = maximum 32MB hard disk size. Therefore, to allow bigger disks, their size had to be splitted in parts < 32MB, so FDISK allowed 1 primary partition, and 1 extended partition, who could be subdivided in up to 4 subpartitions, what gave max 160MB HD (at this time, this was enormous and very expensive !!) Since DOS 4.XX, it was introduced the BIG primary partition, with 32-bit sector numbering, what pushed the limit to 4 terabytes (still in use) in a sole partition. Beside this, it gives not only DOS partition types, there are NOVELL, UNIX, XENIX, etc...

Here are a couple of great sites to get definitions to any computer specific questions: www.whatis.com www.webopedia.com