<rant> There are quite a few "eSata brackets" out there that connect to an SATA connector on the motherboard and present a physical eSata connection outside the case. In my opinion, these are out of spec and should not be used. The electrical specifications for SATA and Esata are different. They overlap, so this lash-up frequently works, but this should not be relied on.
To find out if your machine / motherboard actually supports eSata, if you have the manual, read it. </rant>