Knoppix can often give access to a windows partition even when windows has problems with it, but this is really a windows problem, not a Knoppix or Linux problem, and if the data is deleted or too damaged Knoppix simply may not be able to read it. There are some Live CD that are designed specifically for data recovery and forensic data work, such as Helix, that might help. But you may need to start accepting that your data has moved on to that big bit bucket in the sky if that doesn't help.