Many of them use flash drives...
flash drives as their main hard drives? so they just clone for all of them?
Still curious....
Yep; they generally use flash drives loaded with something like BAMT - a dedicated BTC mining Linux distro - or some other Linux distribution with all of the drivers, applications, and settings needed to mine.
Most of the time, these miners don't have their own wallets: instead, they connect to a pool, so all they need is a miner and an internet connection.