give a look at: http://linux-ntfs.sourceforge.net/status.html

unfortunately what u are looking for (ntdefrag) is still to develop, but u can see what u can do.

anyway... are u sureit's a good idea to defrag win2k by linux???
bad idea at all i think, just be happy to read and write data. to do this (write on ntfs) u need to recompile ur kernel with write support.
regards, pacho