you can get the MK802 for $80 which has 512 mb of ram or get the more pricey one which has 1gb of ram
if you do go through and buy one, get it from aliexpress.com (buy straight from china) i post on the forums here all about the MK802 Mini PC
Keyboard is gonna be like $30 and mouse is about $20 (Depends what you get, i look for the cheapest)
and bam, a great deal for a hacking computer.
The Mini Pc accepts Mirco SD cards up to 32GB, thats your HD right there.