Well when you delete a file from the recycle bin, its not truly lost. You cant just delete a file, so what windows does is it marks it as space that can be overwritten and what your told is you have 45 gigs free, but what it really means. Is you have 45 gigs of othr stuff that is ready to be overwritten
Thats how sometimes police detectives can identify lost data on which a computer was used to commit the crime.
I wouldnt reccomend that program though, http://www.winrecovery.com/undelete/?rid=google&kid=wu0401