HotSwap!
http://mt-naka.com/hotswap/index_enu.htm
For some stupid reason, MS OS's don't give you the "safely remove hardware" little green arrow for eSATA and SATA drives like they do for USB attached drives, despite the fact that SATA technology includes hotswapping as a feature, just like USB does.
This is a simple little app that allows you to easily hotswap SATA/eSATA drives from the majority of motherboards/eSATA cards that I've tried it with. It puts a red arrow in the clock tray that looks like the green arrow you're used to. You can use it to safely remove (and add) SATA and eSATA drives without shutting down the computer.