Anyway, 2 questions, where did you get your fan and if you're mining using a Erupter, do you even really need a fast computer or can you just use a cheap, semi-crappy desktop?
Fan came from Amazon:
http://www.amazon.co.uk/gp/product/B003XN24GY/ -- It will be available on Amazon US or whatever location you are.
I have my 6 block erupters into the DLink DHUB-H7 which is hooked to a raspberry Pi. The Pi does everything to do with the block erupters (it runs cgminer).
So in terms of cost you're looking at $20-30 for the hub, $35 for the pi and whatever the block erupters cost you. Pretty cheap and nice and easy to setup.
This was my original setup:
https://i.imgur.com/Rj8vzwt.jpg* The LCD screen is an Adafruit LCD kit for the Raspberry Pi and is not critical to mining. I just like to see the hashrate easily.
* The hub was some crappy USB 2.0 powered hub but could only support 4 block erupters (2Amp power adapter).
This is my current setup:
https://i.imgur.com/zl81Lgu.jpg* Same LCD screen (I can change the colors on it)
* New DLink DHUB-H7 with 3amp power supply
* Fan added from the 2nd usb port on the Pi
This is CGminer hashing away on the Raspberry Pi (via ssh) with 6 block erupters:
https://i.imgur.com/ADJKsSr.pngDeliberately using that version of cgminer as I heard newer ones had problems with the block erupters. However, I've also tried the newest version with no problems.