Here’s a handy little guide to hooking up a mac to Windows Home Server…
The first thing you’ll need is iTimeMachine installed on your Mac. iTimeMachine is a handy donateware utility that lets you trick OS X into thinking that network drives are actually USB-connected drives, and thus eligible to use for Time Machine. Before you can make the image you need for Time Machine to work, you need to collect a little info.
via Tested.