Blank screen no icons

Hello,

big big problem. need help urgently. Last night i put in a flash disk and scanned it with Avast home basic, avast told me it found one virus which it deleted then i opened files on the flash only to get these messages telling infected with Win 32 Tenga virus which i deleted, then they kept on popping up again saying everything was infected,every programmed installed on the comp, it tells me memory infected, i switch off the comp then restart it again on safe mode, i chose an earlier date and it restarts on its own but when i try to log on to a limited user account it opens to a blank screen with wallpaper then logs off without my prompting, i try again to open to the administrator's account which is password protected, it also opens to a blank wallpaper screen. What i would helped with how can i get everything back to normal. I have important files as well as stuff how do i save these things from getting deleted. PLEASE HELP!!!! I'm not tech savy any simple suggestions welcomed. Thank You