Warning: main(class.invitation.php): failed to open stream: No such file or directory in C:\Webs\HCF3\invitations_party.php on line 3

Fatal error: main(): Failed opening required 'class.invitation.php' (include_path='.;C:\Webs\HCF3;C:\Webs\HCF3\_lib\pear;C:\Webs\HCF3\admin;C:\Webs\HCF3\_lib\_base;C:\Webs\HCF3\_lib\_classes') in C:\Webs\HCF3\invitations_party.php on line 3