eSATA Port

I just purchased a Western Digital 1TB DVR expander so that I can xfer movies from my DVR that has limited storage. The h/w requirements state that I must have a "active eSATA port" on my DVR. It apperars my DVR only has a couple of USB ports 2.0m Ethernet conection port and a a couple of IEEE ports. So will this product work for my intended use or shoud I investigate other options and products. I'm assuming I need to verify my computer has the requirred port as well