Hi Geezer207,
A Mini PCI Express slot is a version of the PCI-Express x1 slot for Laptops. It is not used for connecting mSATA drives although they look very similar.
It is generally used for connecting wireless cards. Listed below are certain cards that are used on this port.
WLAN
Intel PRO/Wireless 3945ABG Mini-PCI Express Adapter
Intel PRO/Wireless 4965AGN Mini-PCI Express Adapter
Intel Wifi Link 5100
Intel Wifi Link 5300
Intel WiMAX/WiFi Link 5150
Intel WiMAX/WiFi Link 5350
Intel Centrino Wireless-N 1000
Intel Centrino Advanced-N 6200
Intel Centrino Advanced-N + WiMAX 6250
Intel Centrino Ultimate-N 6300
WWAN
Sierra Wireless MC5720
Sierra Wireless MC5725
Sierra Wireless HSDPA WWAN
Qualcomm Gobi 2000
Other
Intel® Turbo Memory hard drive cache
Wireless USB (UWB)
Hope this helps. Please reply for any further questions.