Cannot Login into computer Trojan Please Help

I just got my internet installed back last December 2011. Recently without any internet security that I have been whining to my parents to get today at 2:20 my computer just went psycho. I disconected the internet and then the computer was opening up files and closing them. I got scared so I pulled the plug. that didn't work either. I went to login in and my password suddenly fills full of dots and every time I try to delete them they retake the spot. then I tried password reset that did not work because it kept cancelling me out. I also tried to re boot did not work. Systems recovery did not work either because I tried to continue but it cancelled me out while selecting different languages. In system change f10 i could not even use the up and down scoll keys it and the only time it would listen was when I pressed escape. What do I do? my computer has been hacked luckilly I never ever did bought anything off that computer and I did try to download a video game off pirate bay but i'm unsure if thats the cause it was probably the fact of leaving it there for trojans to attach themselves to files. I want to re access it so I can get all my microsoft files. I do not even know if I even have my Windows vista box anymore I do not know where my parents put it.

Someone please help. I need my computer for study if I do not have that what will I do!