Cool. However I noticed a couple things:
a) It only deletes music, sounds, images and sprites. It should also delete matrices, objects, vectors, memblocks, cameras, particles, and it should close files.
b) It can only delete one type of thing at a time. Try implementing some kind of parsing so the parameter could be "sprites, images, sounds" and it would delete all three of those things.
c) Change 'wat$' to 'lower$( wat$ )', that way the parameter could be 'Sprites' or 'IMAGES' and it would still compare it properly.
d) The function assumes that you only have a max of 99 things. Make a parameter that lets the user choose the number of objects he has with a parameter, then loop until that number. That way if someone has 10 objects the loop only has to iterate 10 times, and if they have 5000 then they won't be constrained to a 99-iteration loop.
e) You should probably put an 'ExitFunction' at the end of each sub-routine.