Not all cables from your power supply will be plugged in. You should tie back and hide the cables that you aren't using. It's there for additional hardware if you get any. CD/DVD burners can read cd/dvds but not all of them do (usually specified in specs).
As for the eSATA thing, it's just for external hard drives. Usually when you pop out the expansion slots, it's not really going to go back in perfectly but it will go back in. Btw, if you're in college, they usually offer OS to you for cheaper or free.
cheaper dvd burner (with neweggs sexy shipping)
Newegg.com - Sony Optiarc 24X DVD Burner, Bulk Package 24X DVD+R 8X DVD+RW 12X DVD+R DL 24X DVD-R 6X DVD-RW 16X DVD-ROM 48X CD-R 32X CD-RW 48X CD-ROM Black SATA Model AD-7280S-0B - CD / DVD Burners