It is incredible how much your personal information may be found in your computer. Actually, your PC is the best spy on you. It is constantly logging, quietly and accurately, each program you started, document you opened, music or movie you played, each web site you visited, even each printer or other peripheral device you attached. Moreover, it also constantly makes "temporary" copies of any opened file, and not always it erases them when you are through with that file. Contents of deleted files remain on hard drives and can be easily brought back using inexpensive and easily available data recovery utilities. Anyone who can snoop into your computer could make quite an exact profile of you. Such snooping can be made even remotely when you are on the Internet.
Note: Files deleted on SSD devices usually cannot be recovered even if they've not been wiped. Read File Erasure on SSD and HDD devices page for details.
To make the things worse, there is no built-in system routines that might clean all those records and links. On the contrary, Windows does everything possible to keep all that data as long as possible. That is why you need to use R-Wipe & Clean to protect yourself from such snooping.