It is not safe to write to a NTFS partition with Knoppix.
Addedto that, when Windows installs something it almost always makes entries to the "registery", a Windows database in Microsoft's own format that Knoppix does not deal with. Microsoft is generous with their warnings that you don't want to corrupt the registery or it may ruin the Windows install.
Knoppix can be used to recover key data before doing a Windows "reinstall".