Hmmm... good old NTFS eh?
Generally not, as Time Machine doesn't see these straight off the bat - but there is a workaround that does work reliably. I've tried it and it's fine. Since I've bought a Time Capsule that seamlessly provides both wireless comms & 2TB worth of backup area I use this instead now.
NTFS & Time Machine:
http://hciguy.wordpress.com/2010/06/...running-win-7/