Technical background
Undeleting files
Searching deleted files
Recovering from the system drive
How to recover from the system drive without running the installed Windows.

You switched off your computer one way or the other and want to recover files from the system drive. But how? Obviously, you must not boot the original Windows. Booting and running a computer will overwrite deleted files on the system drive. So you need to boot another operating system. But how? There are operating systems available on CD that do not install themselves on the computer. You could boot from such a Live-CD. It is also possible to boot from a USB drive which contains an operating system. It is conceivable that these operating systems will not overwrite deleted files on your original system drive. But you can only be sure, if your original system drive is write protected. It's hard or impossible to write protect internal drives. Finally, as you want to recover data from that drive, you need to run a data recovery software of your choice.

If you are a computer expert, there is an alternative: you can remove the hard disk from the computer and attach it as an external drive to another computer. The advantage being that external drives can be write protected.