well, here is a good place to google for software..
mmm.. well, when you pull something into recycling bin, and then clean from recycling bin, windows doesn't actually erase the file from your harddrive (it's very very hard to erase a file.. as you'll see later).. they just change the first character of the file into a special character, so that the windows can't see it.. and thus assuming the file and all it's associated bytes are deleted.. when you write stuff onto your harddrive, it will overwrite the sector where windows can't see the file.. so you can recover the files deleted a while ago (depends on how much I/O you have from the time you deleted the file to the time you want to recover it).. If you overwrite the sector once or twice, it's very hard to recover the full file.. depends on the file type, it's either useful or useless to recover parts.. for secure delete, you have to overwrite your data 7 times to render it completely unrecoverable. Even format a hard drive cannot delete the files.. with a boot disk and a recovery software (i used to know a very popular recovery software.. now i forgotten as i haven't recovered anything in quite a while..).. When you choose secure delete from norton internet security and such software, they will actually create random data and overwrite the sector several times to ensure actually deleted the files
try google "file recovery software", and try download.com for software names.. usually good quality software of this kind is very very expensive (200-600 at least.. some better software sells for thousands)..