It seems you enabled save actor thumbs without setting a local path, hence putting them all in your C directory
Set the local path to a folder, eg "C:\Actors" and place those 99 folders in there.
To allow XBMC to see them you will need to set the XBMC path to that folder
If XBMC is on the same machine as MC then just enter C:\Actors
If XBMC is on another networked machine then make sure that the actors folder is shared with XBMC, and enter the network path to the folder.
This can be tricky to get right, which is why it is an advanced setting, it is much easier to leave this setting disabled, although browsing movies, and updating XBMC can take a little longer.
Once you have sorted it, you will probably need to rescrape your movies to fix the problem.