Depends upon what internet café business model you are going to establish?
Depends upon your budget and the number of computers you want to start with.
For gaming go to the extreme specs available.
Don’t buy on impulse or recommendations of others, do your homework….take your time before buying….visit as many computer stores as possible and talk to as many people as possible who knows about computers not just the store clerks.
Use the internet to look for the information that you might need.
A driver is a program that lets the operating system communicate with the computer hardware.
Computer parts need a driver because they do not use standard commands. (Ex.: ATI and Nvidia graphic cards do the same jobs, but not the same way). Different operating systems also need different drivers, a driver written for Linux can not be used by
A computer virus is simply a set of computer instructions or computer code that is written by some unscrupulous person. This code is attached to some part of the normal computer operating system or computer program. Instructions in this code tell the computer to perform some task.
Malware , a portmanteau word from the words mal icious and soft ware , is software designed to infiltrate or damage a computer system without the owner's informed consent . The expression is a general term used by computer professionals to mean a variety of forms of hostile, intrusive, or annoying software or program code. 
Spyware is computer software that is installed surreptitiously on a personal computer to intercept or take partial control over the user's interaction with the computer, without the user's informed consent .
It is mainly used to monitor the internet habits of the computer user as to determine his needs and wants