Types of hard drive

Hard drives come in 2 physical sizes, 2.5" for notebooks and 3.5" for PC's, its quite possible to put a 2.5" hard drive in your PC though there is little point in doing so.

2.5" hard drives come in smaller storage capacities than 3.5" drives, as of writing 2.5" drives are available from 40 to 200 Gigabytes, 3.5" drives from 80 to 1000 Gigabytes (1 terabyte)

How big is a Terabyte ?

Big ;) The National Archives of Britain, which hold 900 years of written material, contains nearly 60 terabytes of data, high end PC's are now found with 1.5 to 2 Terabytes of storage, I am not going to work out how many songs you can fit on 1 Terabyte ... but its a lot!

IDE/PATA SATA?

IDE (PATA) drives have been around for a long (in computing terms) time now, and almost all new motherboards still have at least 1 IDE channel available (which allows 2 PATA devices to be attatched), that said, IDE drives are getting very close to end of life, SATA drives are now and will continue to be for the near future the preferred (and faster) hard drive specification.

All new motherboards will have at least 2 SATA connectors (4 is better) don't buy a `new` motherboard that does not have SATA, assuming history repeats itself IDE drives will be available for a few years to come and prices will rise as demand fails, currently PATA and SATA devices have similar pricing