Need Help in Basic Animation

Okay, I'm a complete newbie with animation, and one problem (or is it) I have not yet solved for myself-

After I animate something, and set its keyframe, and play the framed through, I can't lets say, undo the animation without deleeting the object.

For instance- if I make a sphere and cloth, then make the sphere pass through the cloth, but decide that its not the path i want the sphere to take- if i change the path / whatever then the cloth still animated as the first sphere.

Ok, now that I've proven myself as a dumbass can any solve this for me?

It sounds like you are not deleted the cloth cache after changing the aniamtion for the object collidign with the cloth

How do I do that?

Simulation>Delete Cache