If this is snow leopard which should support reading and writing to and from NTFS partitions you can make a backup of the system file in that directory under apples operating system, then go to the system volume information or recovery folder(s) ( one or the other ) and copy the backed up system file over into the relevant directory ( \windows\system32\config ) ensuring it is literally named
SYSTEM or
system without anything pre fixed.
Then reboot and try and boot into windows.
If you are getting the file from the system_volume_information directory , you will need to take owner ship or add yourself and give your own admin account full access rights to the folder which should hopefully trickle down to sub folders
Go into the restore directory ( normally named _restore ) --> Sort it into details view so you can see date / time column, go into the directory that is the latest or nearer the latest one, then go into the snapshort directory
You should now see all of the files named something along the lines of
_Registry_Machine_Sam
The one you are after seeing as it states system is :
_REGISTRY_MACHINE_SYSTEM
You would copy this file to the
\windows\system32\config directory and rename it to just
system
If you have issues with writing or reading to and from an NTFS partition you can install NTFS 3G , reboot and go back into OS X ( apples OS ) and then do the above.
Pretty much following the MS KB when you get these sorts of issues except you are obviously doing it manually through OS X instead of using a batch file to do all the deleting / copying etc
How to recover from a corrupted registry that prevents Windows XP from starting
More or less what I explained above but without doing a snapshot at the end, which you can do
If you're still stuck drop me a pm or I can try and ellaborate on the above if needed