Vista startup olny wallpaper no others?

After a windows update, i tried to startup and when i tried to,there were no 'Welcome' and when i logged in i can only see my wallpaper,no others like explorer.exe and icons, i also tried Ctrl+Alt+Del i can only see a black screen and cannot start task manager.I can startup with safe mode with icons btw.

I am using windows vista home premium,service pack 2