[saltynay]

Originally Posted by Nukem

The smallest you would be able to go would be a micro ATX case, and still let you use standard size parts. There are smaller cases, but then you would limit yourself to certain parts that are made for them.

Newegg.com - COOLER MASTER Centurion Micro ATX 541 RC-541-SKR1 Black Aluminumm bezel, SECC chassis MicroATX Mini Tower Computer Case 380W Power Supply - Retail

something like this would allow for plenty of airflow and still be kinda small, while still being able to upgrade later on without much worry. And since it has a decent PSU included, you could throw in a 7600GT and be able to run most games with it.

limit parts :s how do you mean you can get a micro-itx motherboard with Q6600 and 8800 ultra the cheer size of the gfx card would rather defeat the object however it is still a possibility

Key questions:
How much do you want to spend?
How small do you want? You can build a computer the size of an old school gameboy to the size of an entire building dimensions are very adaptable
Main function? general use
Secondary function? low-end to moderate gaming
Aesthetic considerations?