As you may already know, Windows Vista SP2 and up (includes Windows 7) block raw disk write access. Is there a way, short of patching the kernel, to override that block? So in cygwin I can do e.g. cat ./myfile>/dev/sdc3
Is there a Windows freeware program that you recommend which writes raw images to disk?
You shouldn't be making raw sector-for-sector images of NTFS. The ImageX utility from the Windows Automated Installation Kit (AIK) will do what you're looking for, albeit to image a machine while it's running you'll need to use Volume Shadow Copy to make a snapshot and image the snapshot (somebody has written a crafty little script to do this but I've never tried it, personally).
Edit:
If you're imaging from Linux consider using the
ntfsclone
tool from the ntfsprogs suite. I've used it for years with great success.dd for windows? If you're trying to backup/restore a partition, I'd suggest something like Clonezilla instead. It's going to be a lot more reliable if you can boot the system to another OS before trying to image it. Taking a raw image of a running system may or may not work correctly.