Windows Explorer and Internet Explorer won't launch

I can't open my browser, and Windows Explorer won't
launch to open My Computer or Control Panel or any other
application. I've reinstalled Windows XP and IE6 and the
problem still exists. I can't open System Restore
because I keep getting an error message, and I'm not sure
I have any restore points to return to. The problem
started when I upgraded from RealPlayer to RealOne. Any
ideas? I've got a home network so I still have access to
the net using one of the other computers. Thanks!