I will search on the Internet for the solution. If you don't mind, could you please post your experience with DROBO sparse bundle? That will save me some dough and heartache with EX495.
Drobo has a utility called Time Tamer that automatically creates the sparesbundle for use with Time Machine. You can create it manually - there are lots of tutorials out there - but Time Tamer is really nice. It might require a drobo to be present now that it's an app. It use to be an applescript and worked even if you didn't have a Drobo.
With Lion, a newer version of the Apple File Sharing protocol is required. Windows Server doesn't have AFP support any longer and it will be interesting to see if Microsoft's partner for the Time Machine plugin for WHS 2011 will get a Lion compatible version out any time soon. So, you can run a FreeNAS instance in emulation on your WHS as some have to get Time Machine working with your WHS, or just slap another drive on your Mac Mini for your MBP. I still use WHS for other storage and my central iTunes library. And for that I just configured WHS to auto-login since it runs on a Mediasmart EX490 that doesn't have a keyboard, mouse or monitor on it so security isn't much of an issue for the local console even if someone is in front of the machine