I am trying to install TTO onto my daughter's computer, but I keep getting an error message. The message says: The installer you are trying to use is corrupted or incomplete. This could be the result of a damaged disk, a failed download or a virus. You may want to contact the author of this installer to obtain a new copy. It may be possible to skip this check using the /NCRC command line switch (NOT RECOMMENDED). What should I do? Any advice or suggestions?