when i start up my PC, after my system POSTs, i get the window which prompts me for a user name and password. we haven't set up any settings for both so i just click ok. after that, i get a black screen and the system freezes unless i hit on ctrl+alt+del. this brings up the task manager. i have to choose a new task and type in the location of my windows explorer before i could reach my desktop. how could i fix this and get to my desktop the normal way?..... help please!