SATA2_4 is an Intel port, and is a normal SATA2 connector, it is not eSATA, you can connect any regular SATA drive to it
See here from your manual, it is a regular SATA2 port, and sorry about the SATA2_5 comment, I always forget these boards only have 5 regular Intel SATA ports (2x 6Gb/s and 3 x 3Gb/s)

No worries about being new to setting up a motherboard, we all have to start somewhere! Hope this helps you, and good luck with your Lion OSX setup, sorry I can't help with those issues for you!