XP Control Panel fails to work or programs fail to execute check the shell open command registry settings.
If the following registry key does not look like this
Vista
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\exefile\shell\open\command]
"%1" %*
IsolatedCommand="%1" %*
XP
[HKEY_CLASSES_ROOT\exefile\shell\open\command]
"%1" %*
then your computer may be infected with a different virus.