Windows2000 / prevents critical system files from being deleted or overwritten
Technically it doesn't 'go' anywhere, all 'deleting' a file does is set the computer to not see it anymore, and allow that data to be overwritten. If that data is not overwritten, it is still there, and can be recovered by 'undeleter' software.
All of the "old data" that has not been overwritten can be recovered in Windows and MS-Dos. When a file is deleted in Windows / MS-Dos the first character of the file name is changed to a question mark. This releases the allocated disk space of the deleted file to the free disk space. The data itself is not touched until a program overwrites the data in that allocated space. This is not true of most other operating systems.
The system's registry is overwritten after every successful login and the settings on the initial install were overwritten after the first reboot and login
Yes, it's called dual-boot. Be sure to have Windows installed first so your Linux installer might be able to pick it up and put it in the bootloader, not to mention to keep GRUB from getting overwritten by a monopolistic bootloader by Windows.
no, because once a program is over written it loses all of its memory and can't open anything that was previously there
Since the windows delete and emptying the recycle bin does not completely delete the file you need to use a shredder program so that the file is overwritten with random data and cannot be recovered. You should use CCleaner and select the wipe free space option. You can change the method of deletion in the settings too. I suggest choosing the DOD 5220.22-M method.
Sometimes it happens, especially when you are playing games or stressing your video card with randering and so on. If after rebooting your system working properly it means that it was recovered successfully.
A free on-line file recovery program called Diskdigger, recovered most all deleted files for me, don't use the card until you try to recover the files, or it will be overwritten.
Files deleted from memory cards can often be recovered given the new files were not over written on the old files. If you accidentally deleted pictures from you memory card make sure you don't use the card for further storage so your files don't get overwritten. There are many free software available "zero assumption digital image recovery" is my favorite. Scanning your card with it will give you a list of recoverable files and you can choose which files you want to recover. I have recovered photos and videos deleted 2years ago from my phone's memory card with this method.
You can't. If the document has been overwritten then the old version no longer exists. This is why backups are done.
Tyler.