jigoro 0 Light Poster

somebody help me.. i cannot get rid of a pop up that say something about going to a website and downloading a program. and windows found a critical problem.. it is shown in my attached picture.. please help.

im using windows 2000 without any Service Pack, i used S&D spybot,adaware se and avg.

my spybot detected an alexa somthing and cleaned it but the pop up keeps on popping.

please help