today i was playing on the internet when all of the sudden my wallpaperturned blue, and said i have a trojan on my computer and i needed to scan for viruses. then an antivirus program automatically popped up that i didnt even install i used it anyway and i said i had some but wouldnt clean them unless i register with them. then it wouldnt let me out of the program so i pulled up the task manager but the computer froze up. i rebooted but when i did it came up with an error message about ieexplorer. there is nothing on the desktop and no start bar. Can somebody help me?