Computer starting problem

All the programmes on my computer stopped opening giving me errors messages like rundll32.exe can not load resource DLL and the like. I tried to boot through safe mode but even the safe mode would not show.
At least at the beginning the computer could open but now the process stops at the Welcome window.

My computer is a Toshiba XP pack2. It is not a virus that I am sure. I might have touched something. Please help me.