Blackhawk - Every Once In A While tab

I'm listing the first chord in the chorus as a C7, but I actually take my pinky off the 
string in the 3rd fret and put it on the e string. Sounds perfect, but I don't know what 
call that. I guess it's an augmented chord. If anyone knows what that is called please let me know.

[ Tab from: http://www.guitaretab.com/b/blackhawk/1658.html ]
         G       C           G        D
When the moon is bright on a Saturday night
          G       C            D
There's a million stars in the sky
     G       C        G      D
On a winding road her memory flows
C      G        D
She'll face the fact
C   G           D
She wants to go back

chorus
    C7        G           C       D
She opens her heart to an old memory
    C7         G            D
She closes her eyes and she smiles
     C7             G          D            C
Just ask her if she ever still thinks about me
           G     D         C
She'll say every once in a while
G     D         C
Every once in a while

2nd verse

She tries to forget but she hasn't yet
Not a single day goes by
That feeling again reminds her of when
I held her tight
It felt so right

chorus