Your MB has "Six 32-bit PCI bus slots (support 3.3v/5v PCI bus interface)"
Add in a PCI SATA interface card that has an external SATA (eSATA) port. Here's an example.
Note if you need win7 look for a different card. this card only has XP +vista drivers (no win7) and had this comment
"I contacted tech support and got these directions for XP:
Thank you for your inquiry! I would recommend downloading the latest drivers/software directly from our website (http://www.startech.com/item-download/PCIESATA2I-1-Port-eSATA-1-Port-SATA-PCI-Controller-Adapter-Card.aspx).
The path to the 32 bit XP driver (without software) is PCIESATA2I/VRAIDDrv/XP/x86." http://www.newegg.com/Product/Product.aspx?Item=N82E16815158167