It has been months for some files showing up as unrecoverable yet, dispite numerous wipes and defrags, the files still show in the list. I assume recuva is just reporting what it finds in Windows but the question is, where does windows keep the info and how/when will some files ever drop from the list.
File names and info are held (on an NTFS disk) as entries in the MFT (Master File Table). When a file is deleted the entry is flagged as deleted but not removed, even though the file data on the disk may have long gone. A normal scan with Recuva will find these deleted file entries, no matter how many times the file data has been overwritten.
A defrag will consolidate fragments of the MFT, but not remove the deleted entries. The MFT will never shrink in size, according to M/S.
When a new file is created Windows will look for the first available slot in the MFT containing a deleted entry and use that. The file name and information will be overwritten and gone forever. Deleted entries at the front of the MFT will be overwritten first, whilst some entries at the far end may last for ever.
Installing SP3 purged most of the old stuff from the MFT on my pc, replacing them with countless installation files.