Just to be sure, you are putting the phone in to download mode before connecting it to the computer right? Your first post indicates that the sd card window pops up which shouldn't happen if you connect in download mode. Power off phone, hold volume down and power, then select volume up. After that connect phone and odin will see it.
Phones & Tablets: Galaxy S4, Galaxy Note 8", Evo 4g LTE, Evo 3D, Acer Iconia A500, Samsung Galaxy Tab 2 10.1, Ipad 2, Nabi 2,
Rom: Rooted Stock Odexed, Hotspot Mod, Xposed, Wanum