sasmfb:
They already gave you that answer... Clean Audio.
Delete the .wrk file and the run Clean Audio. It locates all the .wav files that are no longer associated with any projects and asks if you want to delete them. Since you have deleted the .wrk file, the .wav's have no association any longer and will show on the list to be deleted. Just choose 'yes'. However, make sure your .bun's are working first. (BTW, make sure you remove the deleted .wrk file from your recycle bin, otherwise CW still associates the .wav's with the copy in your recycle bin and they won't show up in the Clean Audio function.)
Not sure whether this function also deletes the picture files (.wov's). There are generally smaller though and not as much a concern as the .wav's. However, if you want, you can delete all of the picture files manually. Cakewalk will simply redraw them as necessary.
Anyone happen to know if Clean Audio also erases the associated picture files?