MotherBoard Form Factors

atx and micro atx are current boards; btx is no longer used on newer boards. The rest is for some proprietary boards and obsolete stuff; for example, an old dell is for sale on craiglist for only $15; the reason it's so cheap is that it uses a pentium III cpu and windows 98, and the case won't work with atx unless you physically modify it.

Can you elaborate each one???

PC-XT Is a really old IBM Machine Type number 5160 released on March 8, 1983
http://en.wikipedia.org/wiki/IBM_Personal_Computer_XT

Full AT: Old IBM Motherboard form factor commonly used in the 80's. 12" wide by 13.8" deep.
http://www.computerhope.com/jargon/f/fullat.htm

Baby AT: Old IBM motherboard form factor used in the late 80's and early 90's. 12" wide by 8" deep.
http://en.wikipedia.org/wiki/AT_(form_factor)

ATX: Most commonly used form factor. Introduced in 95 is still used today. Standard size is 12" by 9.6"
http://en.wikipedia.org/wiki/ATX

Micro -ATX: Another commonly used current form factor released in 97. 9.6" by 9.6"
http://en.wikipedia.org/wiki/MicroATX

LPX: A form factor used in the 90's but was never really common. Used a riser in the center of the board for PCI cards. 12" by 9"
http://en.wikipedia.org/wiki/LPX_(form_factor)

NLX: A newer, smaller upgraded version of LPX. released in 99. 11" by 7"
http://en.wikipedia.org/wiki/NLX_(motherboard_form_factor)

BTX: Designed to replace ATX in 2005, was adopted by Gateway and Dell for proprietary systems. Was never fully adopted, and ATX variations are still used. Main purpose for design was to help with power issues with Pentium 4 systems.
http://en.wikipedia.org/wiki/BTX_(form_factor)

http://en.wikipedia.org/wiki/Computer_form_factor Wikipedia has some good info. You can also click the name of any form factor for more info. You can also google.

Alright, thanks ev1 but I had researched Wikipedia before I posted this question =P