In spite of active firewall, SpyBot S&D, AdAwareSE-Plus, and PC-cillin anti-virus software, something got into my Dell Dimension 4600 and disabled all of the programs and shortcuts.  Whenever I click on any application, a message pops up and says 'there is no program associated with this file; create a file associate in the folders options (or something like that.)  Some programs or shortcuts I have been able to get to work by right-clicking on "open with" and manually adding the program association, but the really important programs like REGEDIT.EXE and System Restore have been completely disabled, even in safe mode.  I am sending this message from my computer at work.  Nothing works... when I try to reinstall WindowsXP Professional from the Dell OS disk, it won't start.  When I try to use the RUN SETUP.EXE, I get a message that says 'windows cannot run this program.  It needs to know what program created it.'   No matter what I try, it's inoperable.  I've gone into setup, changed the boot sequence and tried booting from the utilities CD, and from the Dell OS CD; the green light comes on briefly in the CD drive but nothing happens.  Does anyone have any suggestions on how I can get control of my computer back?!  I purchased it in June 2004 - does it have Symantec's Ghost utility installed?  I tried following the directions on the website for activating it but that doesn't work either.  How can I even reformat the hard drive if I can't get anything to respond?