In the middle of the game while im playing the game minimizes by its self maybe its a problem of the game its not of my computer cause it never happened before playin games it only started when i was playing GW
This happens to me from time to time as well. There might be a program running on your computer that takes precedent over Guild Wars every now and then. instant messangers like MSN and especially aim do this to me a lot.
Get tweakUI, a powertoy from MS (look here - http://www.filehippo.com/download_tweakui.html). Under General/Focus there's a box you can check to prevent programs from being able to steal focus, something IM and chat programs habitually and rudely do.