Processor:
you need a quad core processor to 5 box on any computer. the Intel Core 2 Quad Q6600 is a nice processor and probably the cheapest you are going to get but it will do the job. you can OC it if you want to get better performance but DO NOT do it if you don't know what you are doing it is verey dangerous and can completely ruin your processor/graphics car/ wat ever you are trying to OC.

RAM:
minimum you want 4 gigs of ram but it is soo chea nowadays that you should just go with 8 gigs, its much more efficent - but running 8 gigs will mean that you will have to have vista 64-bit

Graphics card:
probably an nvidia 9800GTX, i have heard alot of good things about this card from others on these forums that use it to 5box. graphics cards are something you definatly don't want to skimp on, if possible i would sudgest getting top of the line if you can afford it, either an nvidia GTX280 or an ATI HD 4870x2 - both are currently the best out but they are kind of pricy.


thats pritty much it, so all in all you basicly just need a quad core processor, 4-8 gigs of ram (8 highly recomended), and a nice graphics card. hope this helps some ^_^