Hay computer people i realy need your help?

i have windows xp sp2, amd atherlon 64bit 4800+ 2gb ram ddr2, 256 pcix card. all of my start menu has gone, icons i cant right click nothing happens,when my windows logs in i get my desktop in a window, in control panel it wont let me click on task bars it says open when i right click but nothing happens please could u help thanks in advance iu need mor in fo e-mail me at wdjace @ hotmail .com