My Computer Is So Annoying

Its a brilliant spec computer, but it becomes so annoying sometimes... When I load it for the first time that day, it firstly takes a century to start up, then when I try to move the mouse it moved very jagged, it will stop then start again etc. And programs take forever to load. Then I reset the computer and everything works great, and I can keep on resetting it for the rest of the day and it will be fine, but the next day it will do the same. Also, sometimes when the computer is running normally all of a sudden the screen will go black and I will have to restart, loosing all of my work from the last save point (this has only started haoppening recently, and ive got a feeling its because I updated my Videos cards driver to the latest version, my video card is an ATI Hercules Radeon 3D Prophet 9700.

Pkease help, this is annoying the hell out of me!