I'm curious as to what damage... The only reference I can find is that if you stop it in the middle or power outage or something.
The Windows Defragment tools can't defragment other filesystems, so there's no need for concern there. Even if you had a program like MacDrive that you could mount your Mac partition in Windows, the deframent tool needs to "get at the guts" of the filesystem, and since NTFS and HFS+ don't speak the same language, it will just error out.
Also Parallels sees the mac, I often do searches with windows on my mac (it's easier to find files and minor differences in them, especially with itunes). So does this apply to that?
thank you..
No, because the way Parallels mounts the Mac partition is akin to connecting to it via a network connection. In short, the host OS handles reads/writes, not the client OS. While the full-blown version of Diskeeper can defragment over a network, the limited version built into Windows can not. Even if it could, Diskeeper requires that a service be installed on the target machine in order to do so. Since the service is geared toward Windows, even that wouldn't work.
So, probably more information than you wanted to know, but that's OK because I like to hear myself speak sometimes
Oh, one more thing - you don't generally need to defragment an HFS+ partition as OS X handles defragment chores on-the-fly. The only time defragmentation is usually needed is when a volume is regularly in use at or near capacity. In those instances, a tool like iDefrag can be run manually against it.
Inevitably, someone will reply with the argument that they feel like their Mac runs faster when they run iDefrag on it - and that's OK, but what I'm relaying above seems to be the consensus of most the threads on the subject. Also, see
Apple's stance on fragmentation.