H Bridge???

Hi

its now friday (cracker jack day) and im looking at what a H-Bridge is but have found some interesting videos on yourube such as,

http://uk.youtube.com/watch?v=OvId3krjEHA

so from the videos the H bridge is an arrangement of MOSFETs in a circut to control the direct of the motor it seems that most people control the speed of the motor with a variable POT ummm this is not really my aim to be honest i want to control the motor with a computer program so I guess i might need an DtoA converter but thants the next thing to look into it, also think im going to need 2 power supplies in the box one for the actuator and the other for the circut I wonder if i can get hold of a computer power supply that might do everything I need, more researh needed