Get a “live CD” of one of the many versions of Linux. Boot from that CD. Use it to save files to another medium- USB stick, over network, whatever.
There is a version available for that specific purpose. It’s called a “Rescue Disk” or similar and can be downloaded and burned to a CD, then used to rescue a Windoze system HD that can’t be accessed otherwise.
You should have one of these live CD’s laying around just for this type of occurance. It’s not “if” it will happen, but “when”. You just hit the “when lottery”.
That’s exactly what I did when this happened to my PC about a month ago. I was able to rescue my files to the USB drive, then reinstalled XP and my software before copying the documents back to the hard drive.
What he said! (Or she, as the case may be.)
I’ve used Linux live CDs to rescue data from failed Windows installs before. I’ve also used Linux to retrieve data from disks that Windows claimed were unreadable.