as for HOW
it doesnt literally delete things, it deletes the directory that tells XP its there, then it writes over it with whatever other program you add
The recycle bin is actually not that interesting, at least to me its not from a technological standpoint. My understanding is that when a file is moved to the recycle bin, nothing happens to the actual file until the bin is empted then the files is deleted. It sort of like a holding place for the marker for the file.