I have a fix. I downloaded exe_xp.com from Unable to Start a Program with an .exe File Extension and run it on the XP machine. I usually do this after I've run unhackme or other rootkit removal software. The exe_xp.com file will reassociate exe files in the registry. This solution has been available since 2004, but I've found it on a lot of the PCs I service lately. I don't use Nortan Antivirus or Mcafee or any other paid virus protection because the infected computers I see have these programs and I have lost confidence in them. My son isn't regretting the move to Windows 7. He loves it.