The title doesn't give the complete picture; a drive is not showing up under Devices, but it is showing up in Disc Utility and in System Preferences>Startup Disc.

Here's the story:

My start up disc was full, so I moved my OS and everything except my really big files (i.e., photo, video and music folders) off my 1 TB HD to a 240 GB SSD.

Everything went great, except that now my computer doesn't recognize the source drive (the 1 TB drive). It doesn't show up anywhere in the Finder window. However, when I launch DiscUtility, it is there and it is mounted. I tried unmounting and remounting it, but still, it doesn't show up on that left column in Finder.

I CAN see my 2 TB backup drive under Devices though.
I can also see the 1 TB drive (aformentioned startup disc) inside MS Word when I browse the hard drive for a file.

I have a 2010 mac pro running OS 10.7.5.

Can anyone tell me what I need to do to get my computer to recognize this drive? Thank you in advance!