When i try to play games such as baldurs gate, shogun, and neverwintger nights on my xp pc, it alwyas slows down whilst the game is open, its always the same length of time between each slow down and its always exactly the same, where is the probelme, and what can be done about it?

I don't know the exact requirements for the games that you are trying to play but I reckon that you are playing on minimum requirements for each. The problem is called "lag" and it happens when your computer cannot handle the application because of slow hardware like your CPU, amount/speed of RAM, video card, etc.