Sometimes a file or folder cannot be moved to the Recycle Bin, and hence cannot be recovered using the Recycle Bin. This occurs when:
1. the Recycle Bin is configured so that to remove files immediately when deleted;
2. file is too large to be placed into the Recycle Bin (larger than the maximum size of the Recycle Bin);
3. file was deleted not by Windows Explorer, but by another program that doesn't move files to the Recycle Bin;
4. a file was deleted by pressing Shift+Del in Windows Explorer, thereby forcing the Recycle Bin to be bypassed;
5. a file was deleted not from an internal hard drive but rather from a removable memory card, an external, or a network drive.
On top of that, the Recycle Bin has the maximum size that can be configured in the Properties of the Recycle Bin (right-click on the Recycle Bin icon and select Properties). Keep in mind that there is a separate Recycle Bin for each hard drive and the Recycle Bin settings (e.g., the maximum size) can be configured separately for each drive. As the Recycle Bin is filled, the oldest files or folders are thrown away to make room for the new ones.
Depending on the filesystem type, the actual removal of a file is implemented in different ways. For example, on NTFS, if nothing has been written on the disk after deleting the file, the file data is intact. But if you use the drive (save new data) then firstly the old file names are deleted (because file name data is stored in a certain place on the disk and reuse constantly) while old file data may still be intact.