Unable typing under windows enviroment

Greeting all,

Currently I have encounter some problem at my OS system (WinME). While I successful bootup a system I can typing on all application, but suddenly the keyboard like malfunction I totally cant type in any things. I try to use notepad and open a command MSDOS, I can type word under this 2 applicaion. I try scan virus but nothing found. Can I know wat wrong of my system. Thx